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Li Y, Frederick RA, George D, Cogan SF, Pancrazio JJ, Bleris L, Hernandez-Reynoso AG. NeurostimML: a machine learning model for predicting neurostimulation-induced tissue damage. J Neural Eng 2024; 21:036054. [PMID: 38885676 DOI: 10.1088/1741-2552/ad593e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 06/17/2024] [Indexed: 06/20/2024]
Abstract
Objective. The safe delivery of electrical current to neural tissue depends on many factors, yet previous methods for predicting tissue damage rely on only a few stimulation parameters. Here, we report the development of a machine learning approach that could lead to a more reliable method for predicting electrical stimulation-induced tissue damage by incorporating additional stimulation parameters.Approach. A literature search was conducted to build an initial database of tissue response information after electrical stimulation, categorized as either damaging or non-damaging. Subsequently, we used ordinal encoding and random forest for feature selection, and investigated four machine learning models for classification: Logistic Regression, K-nearest Neighbor, Random Forest, and Multilayer Perceptron. Finally, we compared the results of these models against the accuracy of the Shannon equation.Main Results. We compiled a database with 387 unique stimulation parameter combinations collected from 58 independent studies conducted over a period of 47 years, with 195 (51%) categorized as non-damaging and 190 (49%) categorized as damaging. The features selected for building our model with a Random Forest algorithm were: waveform shape, geometric surface area, pulse width, frequency, pulse amplitude, charge per phase, charge density, current density, duty cycle, daily stimulation duration, daily number of pulses delivered, and daily accumulated charge. The Shannon equation yielded an accuracy of 63.9% using akvalue of 1.79. In contrast, the Random Forest algorithm was able to robustly predict whether a set of stimulation parameters was classified as damaging or non-damaging with an accuracy of 88.3%.Significance. This novel Random Forest model can facilitate more informed decision making in the selection of neuromodulation parameters for both research studies and clinical practice. This study represents the first approach to use machine learning in the prediction of stimulation-induced neural tissue damage, and lays the groundwork for neurostimulation driven by machine learning models.
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Affiliation(s)
- Yi Li
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States of America
- Center for Systems Biology, The University of Texas at Dallas, Richardson, TX, United States of America
| | - Rebecca A Frederick
- Phil and Penny Knight Campus for Accelerating Scientific Impact, University of Oregon, Eugene, OR, United States of America
| | - Daniel George
- Department of Computer Science, The University of Texas at Dallas, Richardson, TX, United States of America
| | - Stuart F Cogan
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States of America
| | - Joseph J Pancrazio
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States of America
| | - Leonidas Bleris
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States of America
- Center for Systems Biology, The University of Texas at Dallas, Richardson, TX, United States of America
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, TX, United States of America
| | - Ana G Hernandez-Reynoso
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States of America
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2
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Nolta NF, Christensen MB, Tresco PA. Advanced age is not a barrier to chronic intracortical single-unit recording in rat cortex. Front Neurosci 2024; 18:1389556. [PMID: 38817909 PMCID: PMC11138162 DOI: 10.3389/fnins.2024.1389556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Accepted: 05/02/2024] [Indexed: 06/01/2024] Open
Abstract
Introduction Available evidence suggests that as we age, our brain and immune system undergo changes that increase our susceptibility to injury, inflammation, and neurodegeneration. Since a significant portion of the potential patients treated with a microelectrode-based implant may be older, it is important to understand the recording performance of such devices in an aged population. Methods We studied the chronic recording performance and the foreign body response (FBR) to a clinically used microelectrode array implanted in the cortex of 18-month-old Sprague Dawley rats. Results and discussion To the best of our knowledge, this is the first preclinical study of its type in the older mammalian brain. Here, we show that single-unit recording performance was initially robust then gradually declined over a 12-week period, similar to what has been previously reported using younger adult rats and in clinical trials. In addition, we show that FBR biomarker distribution was similar to what has been previously described for younger adult rats implanted with multi-shank recording arrays in the motor cortex. Using a quantitative immunohistochemcal approach, we observed that the extent of astrogliosis and tissue loss near the recording zone was inversely related to recording performance. A comparison of recording performance with a younger cohort supports the notion that aging, in and of itself, is not a limiting factor for the clinical use of penetrating microelectrode recording arrays for the treatment of certain CNS disorders.
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Affiliation(s)
- Nicholas F. Nolta
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States
| | - Michael B. Christensen
- Division of Urology, Department of Surgery, University of Utah School of Medicine, Salt Lake City, UT, United States
- Department of Otolaryngology – Head & Neck Surgery, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Patrick A. Tresco
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States
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3
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Hamani C, Davidson B, Lipsman N, Abrahao A, Nestor SM, Rabin JS, Giacobbe P, Pagano RL, Campos ACP. Insertional effect following electrode implantation: an underreported but important phenomenon. Brain Commun 2024; 6:fcae093. [PMID: 38707711 PMCID: PMC11069120 DOI: 10.1093/braincomms/fcae093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 12/08/2023] [Accepted: 03/26/2024] [Indexed: 05/07/2024] Open
Abstract
Deep brain stimulation has revolutionized the treatment of movement disorders and is gaining momentum in the treatment of several other neuropsychiatric disorders. In almost all applications of this therapy, the insertion of electrodes into the target has been shown to induce some degree of clinical improvement prior to stimulation onset. Disregarding this phenomenon, commonly referred to as 'insertional effect', can lead to biased results in clinical trials, as patients receiving sham stimulation may still experience some degree of symptom amelioration. Similar to the clinical scenario, an improvement in behavioural performance following electrode implantation has also been reported in preclinical models. From a neurohistopathologic perspective, the insertion of electrodes into the brain causes an initial trauma and inflammatory response, the activation of astrocytes, a focal release of gliotransmitters, the hyperexcitability of neurons in the vicinity of the implants, as well as neuroplastic and circuitry changes at a distance from the target. Taken together, it would appear that electrode insertion is not an inert process, but rather triggers a cascade of biological processes, and, as such, should be considered alongside the active delivery of stimulation as an active part of the deep brain stimulation therapy.
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Affiliation(s)
- Clement Hamani
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Harquail Centre for Neuromodulation, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON M4N 3M5, Canada
| | - Benjamin Davidson
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Harquail Centre for Neuromodulation, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON M4N 3M5, Canada
| | - Nir Lipsman
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Harquail Centre for Neuromodulation, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada
- Division of Neurosurgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON M4N 3M5, Canada
| | - Agessandro Abrahao
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Harquail Centre for Neuromodulation, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada
- Division of Neurology, Department of Medicine, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON M4N 3M5, Canada
| | - Sean M Nestor
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Harquail Centre for Neuromodulation, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada
- Department of Psychiatry, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON M4N 3M5, Canada
| | - Jennifer S Rabin
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Harquail Centre for Neuromodulation, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada
- Division of Neurology, Department of Medicine, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON M4N 3M5, Canada
- Rehabilitation Sciences Institute, University of Toronto, Toronto M5G 1V7, Canada
| | - Peter Giacobbe
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Harquail Centre for Neuromodulation, Sunnybrook Health Sciences Centre, Toronto, ON M4N 3M5, Canada
- Department of Psychiatry, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON M4N 3M5, Canada
| | - Rosana L Pagano
- Laboratory of Neuroscience, Hospital Sírio-Libanês, São Paulo, SP CEP 01308-060, Brazil
| | - Ana Carolina P Campos
- Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
- Laboratory of Neuroscience, Hospital Sírio-Libanês, São Paulo, SP CEP 01308-060, Brazil
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4
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Morales AW, Du J, Warren DJ, Fernández-Jover E, Martinez-Navarrete G, Bouteiller JMC, McCreery DC, Lazzi G. Machine learning enables non-Gaussian investigation of changes to peripheral nerves related to electrical stimulation. Sci Rep 2024; 14:2795. [PMID: 38307915 PMCID: PMC10837107 DOI: 10.1038/s41598-024-53284-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 01/30/2024] [Indexed: 02/04/2024] Open
Abstract
Electrical stimulation of the peripheral nervous system (PNS) is becoming increasingly important for the therapeutic treatment of numerous disorders. Thus, as peripheral nerves are increasingly the target of electrical stimulation, it is critical to determine how, and when, electrical stimulation results in anatomical changes in neural tissue. We introduce here a convolutional neural network and support vector machines for cell segmentation and analysis of histological samples of the sciatic nerve of rats stimulated with varying current intensities. We describe the methodologies and present results that highlight the validity of the approach: machine learning enabled highly efficient nerve measurement collection, while multivariate analysis revealed notable changes to nerves' anatomy, even when subjected to levels of stimulation thought to be safe according to the Shannon current limits.
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Affiliation(s)
- Andres W Morales
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, 90089, USA.
| | - Jinze Du
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA, 90089, USA
| | - David J Warren
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, 84112, USA
| | | | | | - Jean-Marie C Bouteiller
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, 90089, USA
- Institute for Technology and Medical Systems (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA, 90089, USA
| | | | - Gianluca Lazzi
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, 90089, USA
- Department of Electrical Engineering, University of Southern California, Los Angeles, CA, 90089, USA
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90089, USA
- Institute for Technology and Medical Systems (ITEMS), Keck School of Medicine, University of Southern California, Los Angeles, CA, 90089, USA
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Meikle SJ, Allison-Walker TJ, Hagan MA, Price NSC, Wong YT. Electrical stimulation thresholds differ between V1 and V2. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023; 2023:1-4. [PMID: 38082908 DOI: 10.1109/embc40787.2023.10340103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Cortical visual prostheses are designed to treat blindness by restoring visual perceptions through artificial electrical stimulation of the primary visual cortex (V1). Intracortical microelectrodes produce the smallest visual percepts and thus higher resolution vision - like a higher density of pixels on a monitor. However, intracortical microelectrodes must maintain a minimum spacing to preserve tissue integrity. One solution to increase the density of percepts is to implant and stimulate multiple visual areas, such as V1 and V2, although the properties of microstimulation in V2 remain largely unexplored. We provide a direct comparison of V1 and V2 microstimulation in two common marmoset monkeys. We find similarities in response trends between V1 and V2 but differences in threshold, neural activity duration, and spread of activity at the threshold current. This has implications for using multi-area stimulation to increase the resolution of cortical visual prostheses.
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6
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Lycke R, Kim R, Zolotavin P, Montes J, Sun Y, Koszeghy A, Altun E, Noble B, Yin R, He F, Totah N, Xie C, Luan L. Low-threshold, high-resolution, chronically stable intracortical microstimulation by ultraflexible electrodes. Cell Rep 2023; 42:112554. [PMID: 37235473 PMCID: PMC10592461 DOI: 10.1016/j.celrep.2023.112554] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 04/08/2023] [Accepted: 05/05/2023] [Indexed: 05/28/2023] Open
Abstract
Intracortical microstimulation (ICMS) enables applications ranging from neuroprosthetics to causal circuit manipulations. However, the resolution, efficacy, and chronic stability of neuromodulation are often compromised by adverse tissue responses to the indwelling electrodes. Here we engineer ultraflexible stim-nanoelectronic threads (StimNETs) and demonstrate low activation threshold, high resolution, and chronically stable ICMS in awake, behaving mouse models. In vivo two-photon imaging reveals that StimNETs remain seamlessly integrated with the nervous tissue throughout chronic stimulation periods and elicit stable, focal neuronal activation at low currents of 2 μA. Importantly, StimNETs evoke longitudinally stable behavioral responses for over 8 months at a markedly low charge injection of 0.25 nC/phase. Quantified histological analyses show that chronic ICMS by StimNETs induces no neuronal degeneration or glial scarring. These results suggest that tissue-integrated electrodes provide a path for robust, long-lasting, spatially selective neuromodulation at low currents, which lessens risk of tissue damage or exacerbation of off-target side effects.
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Affiliation(s)
- Roy Lycke
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA
| | - Robin Kim
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA
| | - Pavlo Zolotavin
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA
| | - Jon Montes
- Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA; Department of Bioengineering, Rice University, Houston, TX 77005, USA
| | - Yingchu Sun
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA
| | - Aron Koszeghy
- Helsinki Institute of Life Science (HiLIFE), University of Helsinki, 00790 Helsinki, Finland
| | - Esra Altun
- Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA; Material Science and NanoEngineering, Rice University, Houston, TX 77005, USA
| | - Brian Noble
- Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA; Applied Physics Program, Rice University, Houston, TX 77005, USA
| | - Rongkang Yin
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA
| | - Fei He
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA
| | - Nelson Totah
- Helsinki Institute of Life Science (HiLIFE), University of Helsinki, 00790 Helsinki, Finland; Faculty of Pharmacy, University of Helsinki, 00790 Helsinki, Finland
| | - Chong Xie
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA; Department of Bioengineering, Rice University, Houston, TX 77005, USA.
| | - Lan Luan
- Department of Electrical and Computer Engineering, Rice University, Houston, TX 77005, USA; Rice Neuroengineering Initiative, Rice University, Houston, TX 77005, USA; Department of Bioengineering, Rice University, Houston, TX 77005, USA.
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7
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Hughes C, Kozai T. Dynamic amplitude modulation of microstimulation evokes biomimetic onset and offset transients and reduces depression of evoked calcium responses in sensory cortices. Brain Stimul 2023; 16:939-965. [PMID: 37244370 PMCID: PMC10330928 DOI: 10.1016/j.brs.2023.05.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 05/15/2023] [Accepted: 05/17/2023] [Indexed: 05/29/2023] Open
Abstract
BACKGROUND Intracortical microstimulation (ICMS) is an emerging approach to restore sensation to people with neurological injury or disease. Biomimetic microstimulation, or stimulus trains that mimic neural activity in the brain through encoding of onset and offset transients, could improve the utility of ICMS for brain-computer interface (BCI) applications, but how biomimetic microstimulation affects neural activation is not understood. Current "biomimetic" ICMS trains aim to reproduce the strong onset and offset transients evoked in the brain by sensory input through dynamic modulation of stimulus parameters. Stimulus induced depression of neural activity (decreases in evoked intensity over time) is also a potential barrier to clinical implementation of sensory feedback, and dynamic microstimulation may reduce this effect. OBJECTIVE We evaluated how bio-inspired ICMS trains with dynamic modulation of amplitude and/or frequency change the calcium response, spatial distribution, and depression of neurons in the somatosensory and visual cortices. METHODS Calcium responses of neurons were measured in Layer 2/3 of visual and somatosensory cortices of anesthetized GCaMP6s mice in response to ICMS trains with fixed amplitude and frequency (Fixed) and three dynamic ICMS trains that increased the stimulation intensity during the onset and offset of stimulation by modulating the amplitude (DynAmp), frequency (DynFreq), or amplitude and frequency (DynBoth). ICMS was provided for either 1-s with 4-s breaks (Short) or for 30-s with 15-s breaks (Long). RESULTS DynAmp and DynBoth trains evoked distinct onset and offset transients in recruited neural populations, while DynFreq trains evoked population activity similar to Fixed trains. Individual neurons had heterogeneous responses primarily based on how quickly they depressed to ICMS, where neurons farther from the electrode depressed faster and a small subpopulation (1-5%) were modulated by DynFreq trains. Neurons that depressed to Short trains were also more likely to depress to Long trains, but Long trains induced more depression overall due to the increased stimulation length. Increasing the amplitude during the hold phase resulted in an increase in recruitment and intensity which resulted in more depression and reduced offset responses. Dynamic amplitude modulation reduced stimulation induced depression by 14.6 ± 0.3% for Short and 36.1 ± 0.6% for Long trains. Ideal observers were 0.031 ± 0.009 s faster for onset detection and 1.33 ± 0.21 s faster for offset detection with dynamic amplitude encoding. CONCLUSIONS Dynamic amplitude modulation evokes distinct onset and offset transients, reduces depression of neural calcium activity, and decreases total charge injection for sensory feedback in BCIs by lowering recruitment of neurons during long maintained periods of ICMS. In contrast, dynamic frequency modulation evokes distinct onset and offset transients in a small subpopulation of neurons but also reduces depression in recruited neurons by reducing the rate of activation.
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Affiliation(s)
- Christopher Hughes
- Department of Bioengineering, University of Pittsburgh, USA; Center for the Neural Basis of Cognition, USA
| | - Takashi Kozai
- Department of Bioengineering, University of Pittsburgh, USA; Center for the Neural Basis of Cognition, USA; Department of Neuroscience, University of Pittsburgh, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; NeuroTech Center, University of Pittsburgh Brain Institute, Pittsburgh, PA, USA.
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8
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Affiliation(s)
- Max Dabagia
- School of Computer Science, Georgia Institute of Technology, Atlanta, GA, USA
| | - Konrad P Kording
- Department of Biomedical Engineering, University of Pennsylvania, Philadelphia, PA, USA
| | - Eva L Dyer
- Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
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9
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Lycke R, Kim R, Zolotavin P, Montes J, Sun Y, Koszeghy A, Altun E, Noble B, Yin R, He F, Totah N, Xie C, Luan L. Low-threshold, high-resolution, chronically stable intracortical microstimulation by ultraflexible electrodes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.20.529295. [PMID: 36865195 PMCID: PMC9980065 DOI: 10.1101/2023.02.20.529295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
Intracortical microstimulation (ICMS) enables applications ranging from neuroprosthetics to causal circuit manipulations. However, the resolution, efficacy, and chronic stability of neuromodulation is often compromised by the adverse tissue responses to the indwelling electrodes. Here we engineer ultraflexible stim-Nanoelectronic Threads (StimNETs) and demonstrate low activation threshold, high resolution, and chronically stable ICMS in awake, behaving mouse models. In vivo two-photon imaging reveals that StimNETs remain seamlessly integrated with the nervous tissue throughout chronic stimulation periods and elicit stable, focal neuronal activation at low currents of 2 μA. Importantly, StimNETs evoke longitudinally stable behavioral responses for over eight months at markedly low charge injection of 0.25 nC/phase. Quantified histological analysis show that chronic ICMS by StimNETs induce no neuronal degeneration or glial scarring. These results suggest that tissue-integrated electrodes provide a path for robust, long-lasting, spatially-selective neuromodulation at low currents which lessen risks of tissue damage or exacerbation of off-target side-effects.
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Affiliation(s)
- Roy Lycke
- Department of Electrical and Computer Engineering; Rice University; Houston; Texas; 77005, United States
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
| | - Robin Kim
- Department of Electrical and Computer Engineering; Rice University; Houston; Texas; 77005, United States
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
| | - Pavlo Zolotavin
- Department of Electrical and Computer Engineering; Rice University; Houston; Texas; 77005, United States
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
| | - Jon Montes
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
- Department of Bioenginering; Rice University; Houston; Texas; 77005, United States
| | - Yingchu Sun
- Department of Electrical and Computer Engineering; Rice University; Houston; Texas; 77005, United States
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
| | - Aron Koszeghy
- Helsinki Institute of Life Science (HiLIFE); University of Helsinki; Helsinki; 00790; Finland
| | - Esra Altun
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
- Material Science and NanoEngineering; Rice University; Houston; Texas; 77005, United States
| | - Brian Noble
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
- Applied Physics Program; Rice University; Houston; Texas; 77005, United States
| | - Rongkang Yin
- Department of Electrical and Computer Engineering; Rice University; Houston; Texas; 77005, United States
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
| | - Fei He
- Department of Electrical and Computer Engineering; Rice University; Houston; Texas; 77005, United States
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
| | - Nelson Totah
- Helsinki Institute of Life Science (HiLIFE); University of Helsinki; Helsinki; 00790; Finland
- Faculty of Pharmacy; University of Helsinki; Helsinki; 00790; Finland
| | - Chong Xie
- Department of Electrical and Computer Engineering; Rice University; Houston; Texas; 77005, United States
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
- Department of Bioenginering; Rice University; Houston; Texas; 77005, United States
| | - Lan Luan
- Department of Electrical and Computer Engineering; Rice University; Houston; Texas; 77005, United States
- Rice Neuroengineering Initiative; Rice University; Houston; Texas; 77005, United States
- Department of Bioenginering; Rice University; Houston; Texas; 77005, United States
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10
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Whitsitt QA, Koo B, Celik ME, Evans BM, Weiland JD, Purcell EK. Spatial Transcriptomics as a Novel Approach to Redefine Electrical Stimulation Safety. Front Neurosci 2022; 16:937923. [PMID: 35928007 PMCID: PMC9344921 DOI: 10.3389/fnins.2022.937923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 06/17/2022] [Indexed: 11/13/2022] Open
Abstract
Current standards for safe delivery of electrical stimulation to the central nervous system are based on foundational studies which examined post-mortem tissue for histological signs of damage. This set of observations and the subsequently proposed limits to safe stimulation, termed the “Shannon limits,” allow for a simple calculation (using charge per phase and charge density) to determine the intensity of electrical stimulation that can be delivered safely to brain tissue. In the three decades since the Shannon limits were reported, advances in molecular biology have allowed for more nuanced and detailed approaches to be used to expand current understanding of the physiological effects of stimulation. Here, we demonstrate the use of spatial transcriptomics (ST) in an exploratory investigation to assess the biological response to electrical stimulation in the brain. Electrical stimulation was delivered to the rat visual cortex with either acute or chronic electrode implantation procedures. To explore the influence of device type and stimulation parameters, we used carbon fiber ultramicroelectrode arrays (7 μm diameter) and microwire electrode arrays (50 μm diameter) delivering charge and charge density levels selected above and below reported tissue damage thresholds (range: 2–20 nC, 0.1–1 mC/cm2). Spatial transcriptomics was performed using Visium Spatial Gene Expression Slides (10x Genomics, Pleasanton, CA, United States), which enabled simultaneous immunohistochemistry and ST to directly compare traditional histological metrics to transcriptional profiles within each tissue sample. Our data give a first look at unique spatial patterns of gene expression that are related to cellular processes including inflammation, cell cycle progression, and neuronal plasticity. At the acute timepoint, an increase in inflammatory and plasticity related genes was observed surrounding a stimulating electrode compared to a craniotomy control. At the chronic timepoint, an increase in inflammatory and cell cycle progression related genes was observed both in the stimulating vs. non-stimulating microwire electrode comparison and in the stimulating microwire vs. carbon fiber comparison. Using the spatial aspect of this method as well as the within-sample link to traditional metrics of tissue damage, we demonstrate how these data may be analyzed and used to generate new hypotheses and inform safety standards for stimulation in cortex.
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Affiliation(s)
- Quentin A. Whitsitt
- Department of Biomedical Engineering, Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, MI, United States
| | - Beomseo Koo
- Department of Biomedical Engineering, Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States
| | - Mahmut Emin Celik
- Department of Electrical and Electronics Engineering, Gazi University, Ankara, Turkey
| | - Blake M. Evans
- Department of Biomedical Engineering, Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, MI, United States
| | - James D. Weiland
- Department of Biomedical Engineering, Biointerfaces Institute, University of Michigan, Ann Arbor, MI, United States
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI, United States
| | - Erin K. Purcell
- Department of Biomedical Engineering, Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, MI, United States
- *Correspondence: Erin K. Purcell,
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11
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Evers J, Sridhar K, Liegey J, Brady J, Jahns H, Lowery M. Stimulation-induced changes at the electrode-tissue interface and their influence on deep brain stimulation. J Neural Eng 2022; 19. [PMID: 35728575 DOI: 10.1088/1741-2552/ac7ad6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 06/21/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE During deep brain stimulation (DBS) the electrode-tissue interface forms a critical path between device and brain tissue. Although changes in the electrical double layer and glial scar can impact stimulation efficacy, the effects of chronic DBS on the electrode-tissue interface have not yet been established. APPROACH In this study, we characterised the electrode-tissue interface surrounding chronically implanted DBS electrodes in rats and compared the impedance and histological properties at the electrode interface in animals that received daily stimulation and in those where no stimulation was applied, up to eight weeks post-surgery. A computational model was developed based on the experimental data, which allowed the dispersive electrical properties of the surrounding encapsulation tissue to be estimated. The model was then used to study the effect of stimulation-induced changes in the electrode-tissue interface on the electric field and neural activation during voltage- and current-controlled stimulation. MAIN RESULTS Incorporating the observed changes in simulations in silico, we estimated the frequency-dependent dielectric properties of the electrical double layer and surrounding encapsulation tissue. Through simulations we show how stimulation-induced changes in the properties of the electrode-tissue interface influence the electric field and alter neural activation during voltage-controlled stimulation. A substantial increase in the number of stimulated collaterals, and their distance from the electrode, was observed during voltage-controlled stimulation with stimulated ETI properties. In vitro examination of stimulated electrodes confirmed that high frequency stimulation leads to desorption of proteins at the electrode interface, with a concomitant reduction in impedance. SIGNIFICANCE The demonstration of stimulation-induced changes in the electrode-tissue interface has important implications for future DBS systems including closed-loop systems where the applied stimulation may change over time. Understanding these changes is particularly important for systems incorporating simultaneous stimulation and sensing, which interact dynamically with brain networks.
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Affiliation(s)
- J Evers
- School of Electrical and Electronic Engineering, University College Dublin, Engineering Building, UCD Belfield, Dublin, Dublin, 4, IRELAND
| | - K Sridhar
- School of Electrical and Electronic Engineering, University College Dublin, Engineering Building, UCD Belfield, Dublin, Dublin, 4, IRELAND
| | - J Liegey
- School of Electrical and Electronic Engineering, University College Dublin, Engineering Building, UCD Belfield, Dublin, Dublin, 4, IRELAND
| | - J Brady
- School of Veterinary Medicine, University College Dublin, Veterinary Science Center, Dublin, 4, IRELAND
| | - H Jahns
- School of Veterinary Medicine, University College Dublin, Veterinary Science Center, Dublin, 4, IRELAND
| | - M Lowery
- School of Electrical, Electronic & Mechancial Engineering, University College Dublin, Engineering & Materials Science Centre, Belfield, Dublin 4, Dublin, 4, IRELAND
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12
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Effects of stimulus pulse rate on somatosensory adaptation in the human cortex. Brain Stimul 2022; 15:987-995. [DOI: 10.1016/j.brs.2022.05.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 05/26/2022] [Accepted: 05/31/2022] [Indexed: 01/01/2023] Open
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13
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Italiano ML, Guo T, Lovell NH, Tsai D. Improving the spatial resolution of artificial vision using midget retinal ganglion cell populations modelled at the human fovea. J Neural Eng 2022; 19. [PMID: 35609556 DOI: 10.1088/1741-2552/ac72c2] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 05/24/2022] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Retinal prostheses seek to create artificial vision by stimulating surviving retinal neurons of patients with profound vision impairment. Notwithstanding tremendous research efforts, the performance of all implants tested to date has remained rudimentary, incapable of overcoming the threshold for legal blindness. To maximize the perceptual efficacy of retinal prostheses, a device must be capable of controlling retinal neurons with greater spatiotemporal precision. Most studies of retinal stimulation were derived from either non-primate species or the peripheral primate retina. We investigated if artificial stimulation could leverage the high spatial resolution afforded by the neural substrates at the primate fovea and surrounding regions to achieve improved percept qualities. APPROACH We began by developing a new computational model capable of generating anatomically accurate retinal ganglion cell (RGC) populations within the human central retina. Next, multiple RGC populations across the central retina were stimulated in-silico to compare clinical and recently proposed neurostimulation configurations based on their ability to improve perceptual efficacy and reduce activation thresholds. MAIN RESULTS Our model uniquely upholds eccentricity-dependent characteristics such as RGC density and dendritic field diameter, whilst incorporating anatomically accurate features such as axon projection and three-dimensional RGC layering, features often forgone in favor of reduced computational complexity. Following epiretinal stimulation, the RGCs in our model produced response patterns in shapes akin to the complex percepts reported in clinical trials. Our results also demonstrated that even within the neuron-dense central retina, epiretinal stimulation using a multi-return hexapolar electrode arrangement could reliably achieve spatially focused RGC activation and could achieve single-cell excitation in 74% of all tested locations. SIGNIFICANCE This study establishes an anatomically accurate three-dimensional model of the human central retina and demonstrates the potential for an epiretinal hexapolar configuration to achieve consistent, spatially confined retinal responses, even within the neuron-dense foveal region. Our results promote the prospect and optimization of higher spatial resolution in future epiretinal implants.
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Affiliation(s)
- Michael Lewis Italiano
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
| | - Tianruo Guo
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
| | - Nigel H Lovell
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
| | - David Tsai
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Sydney, New South Wales, 2052, AUSTRALIA
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14
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Wei C, Wang Y, Pei W, Han X, Lin L, Liu Z, Ming G, Chen R, Wu P, Yang X, Zheng L, Wang Y. Distributed implantation of a flexible microelectrode array for neural recording. MICROSYSTEMS & NANOENGINEERING 2022; 8:50. [PMID: 35572780 PMCID: PMC9098495 DOI: 10.1038/s41378-022-00366-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 01/14/2022] [Accepted: 02/02/2022] [Indexed: 06/15/2023]
Abstract
Flexible multichannel electrode arrays (fMEAs) with multiple filaments can be flexibly implanted in various patterns. It is necessary to develop a method for implanting the fMEA in different locations and at various depths based on the recording demands. This study proposed a strategy for reducing the microelectrode volume with integrated packaging. An implantation system was developed specifically for semiautomatic distributed implantation. The feasibility and convenience of the fMEA and implantation platform were verified in rodents. The acute and chronic recording results provied the effectiveness of the packaging and implantation methods. These methods could provide a novel strategy for developing fMEAs with more filaments and recording sites to measure functional interactions across multiple brain regions.
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Affiliation(s)
- Chunrong Wei
- State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- University of Chinese Academy of Sciences, 100049 Beijing, China
- School of Future Technologies, University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Yang Wang
- State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- School of Microelectronics, University of Sciences and Technology of China, 230000 Hefei, China
| | - Weihua Pei
- State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Xinyong Han
- Institute of Automation, Chinese Academy of Sciences, 100190 Beijing, China
| | - Longnian Lin
- Key Laboratory of Brain Functional Genomics, East China Normal University, 200062 Shanghai, China
| | - Zhiduo Liu
- State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Gege Ming
- State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- University of Chinese Academy of Sciences, 100049 Beijing, China
- School of Future Technologies, University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Ruru Chen
- Brain Machine Fusion Intelligence Institute, 215131 Suzhou, China
| | - Pingping Wu
- University of Chinese Academy of Sciences, 100049 Beijing, China
- School of Future Technologies, University of Chinese Academy of Sciences, 100049 Beijing, China
- Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, 100190 Beijing, China
| | - Xiaowei Yang
- State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
| | - Li Zheng
- State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- University of Chinese Academy of Sciences, 100049 Beijing, China
- School of Future Technologies, University of Chinese Academy of Sciences, 100049 Beijing, China
| | - Yijun Wang
- State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, 100083 Beijing, China
- University of Chinese Academy of Sciences, 100049 Beijing, China
- Chinese Institute for Brain Research, 102206 Beijing, China
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15
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Pandarinath C, Bensmaia SJ. The science and engineering behind sensitized brain-controlled bionic hands. Physiol Rev 2022; 102:551-604. [PMID: 34541898 PMCID: PMC8742729 DOI: 10.1152/physrev.00034.2020] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 09/07/2021] [Accepted: 09/13/2021] [Indexed: 12/13/2022] Open
Abstract
Advances in our understanding of brain function, along with the development of neural interfaces that allow for the monitoring and activation of neurons, have paved the way for brain-machine interfaces (BMIs), which harness neural signals to reanimate the limbs via electrical activation of the muscles or to control extracorporeal devices, thereby bypassing the muscles and senses altogether. BMIs consist of reading out motor intent from the neuronal responses monitored in motor regions of the brain and executing intended movements with bionic limbs, reanimated limbs, or exoskeletons. BMIs also allow for the restoration of the sense of touch by electrically activating neurons in somatosensory regions of the brain, thereby evoking vivid tactile sensations and conveying feedback about object interactions. In this review, we discuss the neural mechanisms of motor control and somatosensation in able-bodied individuals and describe approaches to use neuronal responses as control signals for movement restoration and to activate residual sensory pathways to restore touch. Although the focus of the review is on intracortical approaches, we also describe alternative signal sources for control and noninvasive strategies for sensory restoration.
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Affiliation(s)
- Chethan Pandarinath
- Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia
- Department of Neurosurgery, Emory University, Atlanta, Georgia
| | - Sliman J Bensmaia
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois
- Committee on Computational Neuroscience, University of Chicago, Chicago, Illinois
- Grossman Institute for Neuroscience, Quantitative Biology, and Human Behavior, University of Chicago, Chicago, Illinois
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16
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Stieger KC, Eles JR, Ludwig K, Kozai TDY. Intracortical microstimulation pulse waveform and frequency recruits distinct spatiotemporal patterns of cortical neuron and neuropil activation. J Neural Eng 2022; 19. [PMID: 35263736 DOI: 10.1088/1741-2552/ac5bf5] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 03/09/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Neural prosthetics often use intracortical microstimulation (ICMS) for sensory restoration. To restore natural and functional feedback, we must first understand how stimulation parameters influence the recruitment of neural populations. ICMS waveform asymmetry modulates the spatial activation of neurons around an electrode at 10 Hz; however, it is unclear how asymmetry may differentially modulate population activity at frequencies typically employed in the clinic (e.g. 100 Hz). We hypothesized that stimulation waveform asymmetry would differentially modulate preferential activation of certain neural populations, and the differential population activity would be frequency-dependent. APPROACH We quantified how asymmetric stimulation waveforms delivered at 10 Hz or 100 Hz for 30s modulated spatiotemporal activity of cortical layer II/III pyramidal neurons using in vivo two-photon and mesoscale calcium imaging in anesthetized mice. Asymmetry is defined in terms of the ratio of the duration of the leading phase to the duration of the return phase of charge-balanced cathodal- and anodal-first waveforms (i.e. longer leading phase relative to return has larger asymmetry). MAIN RESULTS Neurons within 40-60µm of the electrode display stable stimulation-induced activity indicative of direct activation, which was independent of waveform asymmetry. The stability of 72% of activated neurons and the preferential activation of 20-90 % of neurons depended on waveform asymmetry. Additionally, this asymmetry-dependent activation of different neural populations was associated with differential progression of population activity. Specifically, neural activity tended to increase over time during 10 hz stimulation for some waveforms, whereas activity remained at the same level throughout stimulation for other waveforms. During 100 Hz stimulation, neural activity decreased over time for all waveforms, but decreased more for the waveforms that resulted in increasing neural activity during 10 Hz stimulation. SIGNIFICANCE These data demonstrate that at frequencies commonly used for sensory restoration, stimulation waveform alters the pattern of activation of different but overlapping populations of excitatory neurons. The impact of these waveform specific responses on the activation of different subtypes of neurons as well as sensory perception merits further investigation.
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Affiliation(s)
- Kevin C Stieger
- Bioengineering, University of Pittsburgh, 300 Technology Dr, Pittsburgh, Pennsylvania, 15219, UNITED STATES
| | - James Regis Eles
- Department of Bioengineering, University of Pittsburgh, 300 Technology Dr, Pittsburgh, Pennsylvania, 15219, UNITED STATES
| | - Kip Ludwig
- Biomedical Engineering and Neurological Surgery, University of Wisconsin Madison, XXX, Madison, Wisconsin, 53706, UNITED STATES
| | - Takashi D Yoshida Kozai
- Department of Bioengineering, University of Pittsburgh, 3501 Fifth Ave, 5059-BST3, Pittsburgh, PA 15213, USA, Pittsburgh, Pennsylvania, 15219, UNITED STATES
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17
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Yan Z, Li K, Shao D, Shen Q, Ding Y, Huang S, Xie Y, Zheng X. Visible-light-responsive reduced graphene oxide/g-C 3N 4/TiO 2 composite nanocoating for photoelectric stimulation of neuronal and osteoblastic differentiation. RSC Adv 2022; 12:8878-8888. [PMID: 35424887 PMCID: PMC8985170 DOI: 10.1039/d2ra00282e] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/08/2022] [Indexed: 11/21/2022] Open
Abstract
rGO/g-C3N4/TiO2 nanocoating was fabricated on Ti-based implant for photoelectric stimulation of bone and nerve repair. The ternary nanocoating exerted greater photoelectric effects on enhancing osteoblastic differentiation and neurite outgrowth.
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Affiliation(s)
- Ziru Yan
- Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Kai Li
- Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Dandan Shao
- Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Qingyi Shen
- Department of Stomatology, Huashan Hospital, Fudan University, Shanghai, China
| | - Yi Ding
- Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China
| | - Shansong Huang
- Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China
| | - Youtao Xie
- Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China
| | - Xuebin Zheng
- Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China
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18
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Meikle SJ, Wong YT. Neurophysiological considerations for visual implants. Brain Struct Funct 2021; 227:1523-1543. [PMID: 34773502 DOI: 10.1007/s00429-021-02417-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 10/17/2021] [Indexed: 11/26/2022]
Abstract
Neural implants have the potential to restore visual capabilities in blind individuals by electrically stimulating the neurons of the visual system. This stimulation can produce visual percepts known as phosphenes. The ideal location of electrical stimulation for achieving vision restoration is widely debated and dependent on the physiological properties of the targeted tissue. Here, the neurophysiology of several potential target structures within the visual system will be explored regarding their benefits and downfalls in producing phosphenes. These regions will include the lateral geniculate nucleus, primary visual cortex, visual area 2, visual area 3, visual area 4 and the middle temporal area. Based on the existing engineering limitations of neural prostheses, we anticipate that electrical stimulation of any singular brain region will be incapable of achieving high-resolution naturalistic perception including color, texture, shape and motion. As improvements in visual acuity facilitate improvements in quality of life, emulating naturalistic vision should be one of the ultimate goals of visual prostheses. To achieve this goal, we propose that multiple brain areas will need to be targeted in unison enabling different aspects of vision to be recreated.
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Affiliation(s)
- Sabrina J Meikle
- Department of Electrical and Computer Systems Engineering, Monash University, 14 Alliance Lane, Clayton, Vic, 3800, Australia
- Department of Physiology and Biomedicine Discovery Institute, Monash University, 14 Alliance Lane, Clayton, Vic, 3800, Australia
- Monash Vision Group, Monash University, 14 Alliance Lane, Clayton, Vic, 3800, Australia
| | - Yan T Wong
- Department of Electrical and Computer Systems Engineering, Monash University, 14 Alliance Lane, Clayton, Vic, 3800, Australia.
- Department of Physiology and Biomedicine Discovery Institute, Monash University, 14 Alliance Lane, Clayton, Vic, 3800, Australia.
- Monash Vision Group, Monash University, 14 Alliance Lane, Clayton, Vic, 3800, Australia.
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19
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McCreery D, Han M, Pikov V, Miller C. Configuring intracortical microelectrode arrays and stimulus parameters to minimize neuron loss during prolonged intracortical electrical stimulation. Brain Stimul 2021; 14:1553-1562. [PMID: 34678487 PMCID: PMC8800486 DOI: 10.1016/j.brs.2021.10.385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 10/18/2021] [Accepted: 10/18/2021] [Indexed: 10/26/2022] Open
Abstract
BACKGROUND Previous studies have shown that neurons of the cerebral cortex can be injured by implantation of, and stimulation with, implanted microelectrodes. OBJECTIVES Objective 1 was to determine parameters of microstimulation delivered through multisite intracortical microelectrode arrays that will activate neurons of the feline cerebral cortex without causing loss of neurons. OBJECTIVE 2 was to determine if the stimulus parameters that induced loss of cortical neurons differed for all cortical neurons vs. the subset of inhibitory neurons expressing parvalbumin. METHODS The intracortical microstimulation was applied for 7 h/day for 20 days (140 h). Microelectrode site areas were 2000 and 4000 μm2, Q was 2-8 nanocoulombs (nC) at 50 Hz, and QD was 50-400 μcoulombs/cm2. RESULTS Neuron loss due to stimulation was minimal at Q = 2 Ncp, but at 8 Ncp, 20%-50% of neurons within 250 μm of the stimulated microelectrodes were lost, compared to unstimulated microelectrodes. Loss was greatest in tissue facing electrode sites. Stimulation-induced loss was similar for neurons labeled for NeuN and for inhibitory neurons expressing parvalbumin. Correlation between neuron loss and QD was not significant. Electrodes in the medullary pyramidal tract recorded neuronal activity evoked by stimulation in the cerebral cortex. The pyramidal neurons were activated by intracortical stimulation of 2 nC/phase. 140 h of microstimulation at 2 nC/phase and 50 Hz induced minimal neuron loss.
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Affiliation(s)
- Douglas McCreery
- Huntington Medical Research Institutes, 686 South Fair Oaks Ave, Pasadena, CA, 91105, USA.
| | - Martin Han
- Dept. of Biomedical Engineering, The University of Connecticut, Storrs, CT, USA.
| | | | - Carol Miller
- Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA.
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20
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Hughes CL, Flesher SN, Weiss JM, Downey JE, Boninger M, Collinger JL, Gaunt RA. Neural stimulation and recording performance in human sensorimotor cortex over 1500 days. J Neural Eng 2021; 18. [PMID: 34320481 DOI: 10.1088/1741-2552/ac18ad] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 07/28/2021] [Indexed: 01/12/2023]
Abstract
Objective.Intracortical microstimulation (ICMS) in somatosensory cortex can restore sensation to people with spinal cord injury. However, the recording quality from implanted microelectrodes can degrade over time and limitations in stimulation longevity have been considered a potential barrier to the clinical use of ICMS. Our objective was to evaluate recording stability of intracortical electrodes implanted in the motor and somatosensory cortex of one person. The electrodes in motor cortex had platinum tips and were not stimulated, while the electrodes in somatosensory cortex had sputtered iridium oxide film (SIROF) tips and were stimulated. Additionally, we measured how well ICMS was able to evoke sensations over time.Approach. We implanted microelectrode arrays with SIROF tips in the somatosensory cortex (SIROF-sensory) of a human participant with a cervical spinal cord injury. We regularly stimulated these electrodes to evoke tactile sensations on the hand. Here, we quantify the stability of these electrodes in comparison to non-stimulated platinum electrodes implanted in the motor cortex (platinum-motor) over 1500 days with recorded signal quality and electrode impedances. Additionally, we quantify the stability of ICMS-evoked sensations using detection thresholds.Main results. We found that recording quality, as assessed by the number of electrodes with high-amplitude waveforms (>100µV peak-to-peak), peak-to-peak voltage, noise, and signal-to-noise ratio, decreased over time on SIROF-sensory and platinum-motor electrodes. However, SIROF-sensory electrodes were more likely to continue to record high-amplitude signals than platinum-motor electrodes. Interestingly, the detection thresholds for stimulus-evoked sensations decreased over time from a median of 31.5μA at day 100-10.4μA at day 1500, with the largest changes occurring between day 100 and 500.Significance. These results demonstrate that ICMS in human somatosensory cortex can be provided over long periods of time without deleterious effects on recording or stimulation capabilities. In fact, the sensitivity to stimulation improved over time.
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Affiliation(s)
- Christopher L Hughes
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Sharlene N Flesher
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Jeffrey M Weiss
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - John E Downey
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, United States of America
| | - Michael Boninger
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Jennifer L Collinger
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America.,Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Robert A Gaunt
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States of America.,Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA, United States of America
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21
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Zheng XS, Tan C, Castagnola E, Cui XT. Electrode Materials for Chronic Electrical Microstimulation. Adv Healthc Mater 2021; 10:e2100119. [PMID: 34029008 PMCID: PMC8257249 DOI: 10.1002/adhm.202100119] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 04/20/2021] [Indexed: 02/06/2023]
Abstract
Electrical microstimulation has enabled partial restoration of vision, hearing, movement, somatosensation, as well as improving organ functions by electrically modulating neural activities. However, chronic microstimulation is faced with numerous challenges. The implantation of an electrode array into the neural tissue triggers an inflammatory response, which can be exacerbated by the delivery of electrical currents. Meanwhile, prolonged stimulation may lead to electrode material degradation., which can be accelerated by the hostile inflammatory environment. Both material degradation and adverse tissue reactions can compromise stimulation performance over time. For stable chronic electrical stimulation, an ideal microelectrode must present 1) high charge injection limit, to efficiently deliver charge without exceeding safety limits for both tissue and electrodes, 2) small size, to gain high spatial selectivity, 3) excellent biocompatibility that ensures tissue health immediately next to the device, and 4) stable in vivo electrochemical properties over the application period. In this review, the challenges in chronic microstimulation are described in detail. To aid material scientists interested in neural stimulation research, the in vitro and in vivo testing methods are introduced for assessing stimulation functionality and longevity and a detailed overview of recent advances in electrode material research and device fabrication for improving chronic microstimulation performance is provided.
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Affiliation(s)
- Xin Sally Zheng
- Department of Bioengineering, University of Pittsburgh, 3501 Fifth Ave. Pittsburgh, Pittsburgh, PA, 15213, USA
| | - Chao Tan
- Department of Bioengineering, University of Pittsburgh, 3501 Fifth Ave. Pittsburgh, Pittsburgh, PA, 15213, USA
| | - Elisa Castagnola
- Department of Bioengineering, University of Pittsburgh, 3501 Fifth Ave. Pittsburgh, Pittsburgh, PA, 15213, USA
| | - Xinyan Tracy Cui
- Department of Bioengineering, University of Pittsburgh, 3501 Fifth Ave. Pittsburgh, Pittsburgh, PA, 15213, USA
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22
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Allison-Walker T, Hagan MA, Price NSC, Wong YT. Microstimulation-evoked neural responses in visual cortex are depth dependent. Brain Stimul 2021; 14:741-750. [PMID: 33975054 DOI: 10.1016/j.brs.2021.04.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 02/26/2021] [Accepted: 04/27/2021] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND Cortical visual prostheses often use penetrating electrode arrays to deliver microstimulation to the visual cortex. To optimize electrode placement within the cortex, the neural responses to microstimulation at different cortical depths must first be understood. OBJECTIVE We investigated how the neural responses evoked by microstimulation in cortex varied with cortical depth, of both stimulation and response. METHODS A 32-channel single shank electrode array was inserted into the primary visual cortex of anaesthetized rats, such that it spanned all cortical layers. Microstimulation with currents up to 14 μA (single biphasic pulse, 200 μs per phase) was applied at depths spanning 1600 μm, while simultaneously recording neural activity on all channels within a response window 2.25-11 ms. RESULTS Stimulation elicited elevated neuronal firing rates at all depths of cortex. Compared to deep sites, superficial stimulation sites responded with higher firing rates at a given current and had lower thresholds. The laminar spread of evoked activity across cortical depth depended on stimulation depth, in line with anatomical models. CONCLUSION Stimulation in the superficial layers of visual cortex evokes local neural activity with the lowest thresholds, and stimulation in the deep layers evoked the most activity across the cortical column. In conjunction with perceptual reports, these data suggest that the optimal electrode placement for cortical microstimulation prostheses has electrodes positioned in layers 2/3, and at the top of layer 5.
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Affiliation(s)
- Tim Allison-Walker
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic, 3800, Australia; ARC Centre of Excellence for Integrative Brain Function, Australia; Monash Vision Group, Monash University, Clayton, Vic, 3800, Australia
| | - Maureen A Hagan
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic, 3800, Australia; ARC Centre of Excellence for Integrative Brain Function, Australia
| | - Nicholas S C Price
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic, 3800, Australia; ARC Centre of Excellence for Integrative Brain Function, Australia
| | - Yan T Wong
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic, 3800, Australia; ARC Centre of Excellence for Integrative Brain Function, Australia; Department of Electrical and Computer Systems Engineering, Monash University, Clayton, Vic, 3800, Australia; Monash Vision Group, Monash University, Clayton, Vic, 3800, Australia.
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Ersöz A, Kim I, Han M. Maximizing Charge Injection Limits of Iridium Oxide Electrodes with a Programmable Anodic Bias Circuit. INTERNATIONAL IEEE/EMBS CONFERENCE ON NEURAL ENGINEERING : [PROCEEDINGS]. INTERNATIONAL IEEE EMBS CONFERENCE ON NEURAL ENGINEERING 2021; 2021:540-543. [PMID: 34925702 PMCID: PMC8674787 DOI: 10.1109/ner49283.2021.9441282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Efficacious stimulation of neural tissues requires high charge injection capacity while minimizing electrode polarization. Applying anodic bias on certain electrode materials is a way to enhance charge injection both in vitro and in vivo. We developed an embedded neurostimulator system that enabled a digital control of user-defined bias levels, without requiring a potentiometer or external voltage source. Comparison of charge injection with and without anodic-bias, as well as at different bias potentials were conducted in phosphate-buffered saline with Blackrock iridium oxide microelectrodes. Results showed that a nine-fold increase in current intensity and charge injection capacity, was achieved with a 0.7 V anodic bias and within electrochemically safe limits.
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Affiliation(s)
- Alpaslan Ersöz
- Biomedical Engineering Department, University of Connecticut, Storrs, CT 06269 USA
| | - Insoo Kim
- Department of Medicine and Division of Occupational and Environmental Medicine, University of Connecticut, Farmington, CT 06030 USA
| | - Martin Han
- Biomedical Engineering Department, University of Connecticut, Storrs, CT 06269 USA
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Evers J, Lowery M. The Active Electrode in the Living Brain: The Response of the Brain Parenchyma to Chronically Implanted Deep Brain Stimulation Electrodes. Oper Neurosurg (Hagerstown) 2021; 20:131-140. [PMID: 33074305 DOI: 10.1093/ons/opaa326] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 08/10/2020] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Deep brain stimulation is an established symptomatic surgical therapy for Parkinson disease, essential tremor, and a number of other movement and neuropsychiatric disorders. The well-established foreign body response around implanted electrodes is marked by gliosis, neuroinflammation, and neurodegeneration. However, how this response changes with the application of chronic stimulation is less well-understood. OBJECTIVE To integrate the most recent evidence from basic science, patient, and postmortem studies on the effect of such an "active" electrode on the parenchyma of the living brain. METHODS A thorough and in-part systematic literature review identified 49 papers. RESULTS Increased electrode-tissue impedance is consistently observed in the weeks following electrode implantation, stabilizing at approximately 3 to 6 mo. Lower impedance values are observed around stimulated implanted electrodes when compared with unstimulated electrodes. A temporary reduction in impedance has also been observed in response to stimulation in nonhuman primates. Postmortem studies from patients confirm the presence of a fibrous sheath, astrocytosis, neuronal loss, and neuroinflammation in the immediate vicinity of the electrode. When comparing stimulated and unstimulated electrodes directly, there is some evidence across animal and patient studies of altered neurodegeneration and neuroinflammation around stimulated electrodes. CONCLUSION Establishing how stimulation influences the electrical and histological properties of the surrounding tissue is critical in understanding how these factors contribute to DBS efficacy, and in controlling symptoms and side effects. Understanding these complex issues will aid in the development of future neuromodulation systems that are optimized for the tissue environment and required stimulation protocols.
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Affiliation(s)
- Judith Evers
- School of Electrical and Electronic Engineering, University College Dublin, Dublin, Ireland.,CÚRAM SFI Research Centre for Medical Devices, National University of Ireland Galway, Galway, Ireland
| | - Madeleine Lowery
- School of Electrical and Electronic Engineering, University College Dublin, Dublin, Ireland.,CÚRAM SFI Research Centre for Medical Devices, National University of Ireland Galway, Galway, Ireland
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Ryu SB, Paulk AC, Yang JC, Ganji M, Dayeh SA, Cash SS, Fried SI, Lee SW. Spatially confined responses of mouse visual cortex to intracortical magnetic stimulation from micro-coils. J Neural Eng 2020; 17:056036. [PMID: 32998116 DOI: 10.1088/1741-2552/abbd22] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Electrical stimulation via microelectrodes implanted in cortex has been suggested as a potential treatment for a wide range of neurological disorders. Despite some success however, the effectiveness of conventional electrodes remains limited, in part due to an inability to create specific patterns of neural activity around each electrode and in part due to challenges with maintaining a stable interface. The use of implantable micro-coils to magnetically stimulate the cortex has the potential to overcome these limitations because the asymmetric fields from coils can be harnessed to selectively activate some neurons, e.g. vertically-oriented pyramidal neurons while avoiding others, e.g. horizontally-oriented passing axons. In vitro experiments have shown that activation is indeed confined with micro-coils but their effectiveness in the intact brain of living animals has not been evaluated. APPROACH To assess the efficacy of stimulation, a 128-channel custom recording microelectrode array was positioned on the surface of the visual cortex (ECoG) in anesthetized mice and responses to magnetic and electric stimulation were compared. Stimulation was delivered from electrodes or micro-coils implanted through a hole in the center of the recording array at a rate of 200 pulses per second for 100 ms. MAIN RESULTS Both electric and magnetic stimulation reliably elicited cortical responses, although activation from electric stimulation was spatially expansive, often extending more than 1 mm from the stimulation site, while activation from magnetic stimulation was typically confined to a ∼300 µm diameter region around the stimulation site. Results were consistent for stimulation of both cortical layer 2/3 and layer 5 as well as across a range of stimulus strengths. SIGNIFICANCE The improved focality with magnetic stimulation suggests that the effectiveness of cortical stimulation can be improved. Improved focality may be particularly attractive for cortical prostheses that require high spatial resolution, e.g. devices that target sensory cortex, as it may lead to improved acuity.
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Affiliation(s)
- Sang Baek Ryu
- Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States of America
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Frederick RA, Meliane IY, Joshi-Imre A, Troyk PR, Cogan SF. Activated iridium oxide film (AIROF) electrodes for neural tissue stimulation. J Neural Eng 2020; 17:056001. [PMID: 32947268 DOI: 10.1088/1741-2552/abb9bf] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Iridium oxide films are commonly used as a high charge-injection electrode material in neural devices. Yet, few studies have performed in-depth assessments of material performance versus film thickness, especially for films grown on three-dimensional (instead of planar) metal surfaces in neutral pH electrolyte solutions. Further, few studies have investigated the driving voltage requirements for constant-current stimulation using activated iridium oxide (AIROF) electrodes, which will be a key constraint for future use in wirelessly powered neural devices. APPROACH In this study, iridium microwire probes were activated by repeated potential pulsing in room temperature phosphate buffered saline (pH 7.1-7.3). Electrochemical measurements were recorded in three different electrolyte conditions for probes with different geometric surface areas (GSAs) as the AIROF thickness was increased. MAIN RESULTS Maintaining an anodic potential bias during the inter-pulse interval was required for AIROF electrodes to deliver charge levels considered necessary for neural stimulation. Potential pulsing for 100-200 cycles was sufficient to achieve charge injection levels of 2.5 mC cm-2 (50 nC/phase in a biphasic pulse) in PBS with 2000 µm2 iridium probes. Increasing the electrode surface area to 3000 µm2 and 4000 µm2 significantly increased charge-injection capacity, reduced the driving voltage required to deliver a fixed amount of charge, and reduced polarization of the electrodes during constant-current pulsing. SIGNIFICANCE This study establishes methods for choosing an activation protocol and a desired GSA for three-dimensional iridium electrodes suitable for neural tissue insertion and stimulation, and provides guidelines for evaluating electrochemical performance of AIROF using model saline solutions.
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Affiliation(s)
- Rebecca A Frederick
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States of America
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Allison-Walker TJ, Ann Hagan M, Chiang Price NS, Tat Wong Y. Local field potential phase modulates neural responses to intracortical electrical stimulation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:3521-3524. [PMID: 33018763 DOI: 10.1109/embc44109.2020.9176186] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Cortical visual prostheses could one day help restore sight to the blind by targeting the visual cortex with electrical stimulation. However, power consumption and limited spatial resolution impose limits on performance, while large amounts of electrical charge sometimes necessary to evoke phosphenes can cause seizures. Here, we propose the use of the local field potential as a control signal for the timing of stimulation to reduce charge requirements. In Sprague-Dawley rats, visual cortex was electrically stimulated at random times, and neural responses recorded. Electrical stimulation at specific phases of the local field potential required smaller amounts of charge to elicit spikes than naïve stimulation. Incorporating this into prosthesis design could improve their safety and efficacy.
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Stieger KC, Eles JR, Ludwig KA, Kozai TDY. In vivo microstimulation with cathodic and anodic asymmetric waveforms modulates spatiotemporal calcium dynamics in cortical neuropil and pyramidal neurons of male mice. J Neurosci Res 2020; 98:2072-2095. [PMID: 32592267 DOI: 10.1002/jnr.24676] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 05/26/2020] [Accepted: 05/27/2020] [Indexed: 12/12/2022]
Abstract
Electrical stimulation has been critical in the development of an understanding of brain function and disease. Despite its widespread use and obvious clinical potential, the mechanisms governing stimulation in the cortex remain largely unexplored in the context of pulse parameters. Modeling studies have suggested that modulation of stimulation pulse waveform may be able to control the probability of neuronal activation to selectively stimulate either cell bodies or passing fibers depending on the leading polarity. Thus, asymmetric waveforms with equal charge per phase (i.e., increasing the leading phase duration and proportionately decreasing the amplitude) may be able to activate a more spatially localized or distributed population of neurons if the leading phase is cathodic or anodic, respectively. Here, we use two-photon and mesoscale calcium imaging of GCaMP6s expressed in excitatory pyramidal neurons of male mice to investigate the role of pulse polarity and waveform asymmetry on the spatiotemporal properties of direct neuronal activation with 10-Hz electrical stimulation. We demonstrate that increasing cathodic asymmetry effectively reduces neuronal activation and results in a more spatially localized subpopulation of activated neurons without sacrificing the density of activated neurons around the electrode. Conversely, increasing anodic asymmetry increases the spatial spread of activation and highly resembles spatiotemporal calcium activity induced by conventional symmetric cathodic stimulation. These results suggest that stimulation polarity and asymmetry can be used to modulate the spatiotemporal dynamics of neuronal activity thus increasing the effective parameter space of electrical stimulation to restore sensation and study circuit dynamics.
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Affiliation(s)
- Kevin C Stieger
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.,Center for the Neural Basis of Cognition, University of Pittsburgh, Carnegie Mellon University, Pittsburgh, PA, USA
| | - James R Eles
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Kip A Ludwig
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, WI, USA.,Department of Neurological Surgery, University of Wisconsin Madison, Madison, WI, USA.,Wisconsin Institute for Translational Neuroengineering (WITNe), Madison, WI, USA
| | - Takashi D Y Kozai
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.,Center for the Neural Basis of Cognition, University of Pittsburgh, Carnegie Mellon University, Pittsburgh, PA, USA.,Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA.,McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.,NeuroTech Center, University of Pittsburgh Brain Institute, Pittsburgh, PA, USA
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Chen J, Poulaki V, Kim SJ, Eldred WD, Kane S, Gingerich M, Shire DB, Jensen R, DeWalt G, Kaplan HJ, Rizzo JF. Implantation and Extraction of Penetrating Electrode Arrays in Minipig Retinas. Transl Vis Sci Technol 2020; 9:19. [PMID: 32821491 PMCID: PMC7401973 DOI: 10.1167/tvst.9.5.19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 12/31/2019] [Indexed: 12/12/2022] Open
Abstract
Purpose This work was motivated by the goals of demonstrating methods to fabricate and implant large numbers of penetrating arrays into the retina and the feasibility of extraction. Methods Arrays of inactive, three-dimensional (3D) SU-8 structures were microfabricated onto 13-µm polyimide substrates. Standard vitreoretinal surgical techniques were used with an ab externo approach for subretinal implantation of arrays in 12 mini-pigs. In the first three surgeries, different post-geometries were explored, while a preferred design (128-µm tall, 30-µm diameter, 200-µm spacing) was used for the remaining nine implantations. Two arrays were extracted. Funduscopy, optical coherence tomography (OCT) and immunohistochemistry of the retinae were performed. The unoperated eyes and tissue far from implantation served as controls. A thirteenth pig was implanted with a planar array. Results Ten implant surgeries had no significant complication, and two arrays were successfully extracted. One retinal tear occurred after implantation due to too long posts in an early surgery. In “successful” cases, OCT showed close apposition of the arrays to the retina and integration of the posts, the tops of which were positioned at the junction of the inner plexiform and ganglion cells, without significant gliosis. Conclusions These results provide a proof-of-concept that relatively large numbers of 3D posts can be implanted into, and extracted from, the retina of mini-pigs. Our surgical numbers were relatively small, especially for the extractions, and our conclusions must be viewed with that limitation. Our methods are applicable for human surgeries. Translational Relevance This study provides results of implantation and extraction of relatively large numbers of 3D posts from the retina of minipig eyes. If similar technology were used in humans, a 3D array of this type should lower perceptual thresholds, provide safer long-term stimulation, and perhaps provide better perceptual outcomes.
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Affiliation(s)
- Jinghua Chen
- Department of Ophthalmology, University of Florida, College of Medicine, Gainesville, FL, USA
| | - Vasiliki Poulaki
- Boston VA Healthcare System, Ophthalmology, Jamaica Plain, Boston, MA, USA
| | - Seong-Joon Kim
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea
| | | | | | | | | | - Ralph Jensen
- Boston VA Healthcare System, Ophthalmology, Jamaica Plain, Boston, MA, USA
| | - Gloria DeWalt
- Department of Biology, Boston University, Boston, MA, USA
| | - Henry J Kaplan
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY, USA
| | - Joseph F Rizzo
- Department of Ophthalmology, Harvard Medical School and the Massachusetts Eye and Ear, Boston, MA, USA
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Foroushani AN, Neupane S, De Heredia Pastor P, Pack CC, Sawan M. Spatial resolution of local field potential signals in macaque V4. J Neural Eng 2020; 17:026003. [PMID: 32023554 DOI: 10.1088/1741-2552/ab7321] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
OBJECTIVE An important challenge for the development of cortical visual prostheses is to generate spatially localized percepts of light, using artificial stimulation. Such percepts are called phosphenes, and the goal of prosthetic applications is to generate a pattern of phosphenes that matches the structure of the retinal image. A preliminary step in this process is to understand how the spatial positions of phosphene-like visual stimuli are encoded in the distributed activity of cortical neurons. The spatial resolution with which the distributed responses discriminate positions puts a limit on the capability of visual prosthesis devices to induce phosphenes at multiple positions. While most previous prosthetic devices have targeted the primary visual cortex, the extrastriate cortex has the advantage of covering a large part of the visual field with a smaller amount of cortical tissue, providing the possibility of a more compact implant. Here, we studied how well ensembles of Local Field Potentials (LFPs) and Multiunit activity (MUA) responses from extrastriate cortical visual area V4 of a behaving macaque monkey can discriminate between two-dimensional spatial positions. APPROACH We used support vector machines (SVM) to determine the capabilities of LFPs and MUA to discriminate responses to phosphene-like stimuli (probes) at different spatial separations. We proposed a selection strategy based on the combined responses of multiple electrodes and used the linear learning weights to find the minimum number of electrodes for fine and coarse discriminations. We also measured the contribution of correlated trial-to-trial variability in the responses to the discrimination performance for MUA and LFP. MAIN RESULTS We found that despite the large receptive field sizes in V4, the combined responses from multiple sites, whether MUA or LFP, are capable of fine and coarse discrimination of positions. Our electrode selection procedure significantly increased discrimination performance while reducing the required number of electrodes. Analysis of noise correlations in MUA and LFP responses showed that noise correlations in LFPs carry more information about spatial positions. SIGNIFICANCE This study determined the coding strategy for fine discrimination, suggesting that spatial positions could be well localized with patterned stimulation in extrastriate area V4. It also provides a novel approach to build a compact prosthesis with relatively few electrodes, which has the potential advantage of reducing tissue damage in real applications.
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Affiliation(s)
- Armin Najarpour Foroushani
- PolyStim Neurotechnology Lab., Institute of Biomedical Engineering, Polytechnique Montreal, Montreal, QC, Canada. Author to whom any correspondence should be addressed
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Eles JR, Kozai TDY. In vivo imaging of calcium and glutamate responses to intracortical microstimulation reveals distinct temporal responses of the neuropil and somatic compartments in layer II/III neurons. Biomaterials 2020; 234:119767. [PMID: 31954232 DOI: 10.1016/j.biomaterials.2020.119767] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 12/22/2019] [Accepted: 01/05/2020] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Intracortical microelectrode implants can generate a tissue response hallmarked by glial scarring and neuron cell death within 100-150 μm of the biomaterial device. Many have proposed that any performance decline in intracortical microstimulation (ICMS) due to this foreign body tissue response could be offset by increasing the stimulation amplitude. The mechanisms of this approach are unclear, however, as there has not been consensus on how increasing amplitude affects the spatial and temporal recruitment patterns of ICMS. APPROACH We clarify these unknowns using in vivo two-photon imaging of mice transgenically expressing the calcium sensor GCaMP6s in Thy1 neurons or virally expressing the glutamate sensor iGluSnFr in neurons. Calcium and neurotransmitter activity are tracked in the neuronal somas and neuropil during long-train stimulation in Layer II/III of somatosensory cortex. MAIN RESULTS Neural calcium activity and glutamate release are dense and strongest within 20-40 μm around the electrode, falling off with distance from the electrode. Neuronal calcium increases with higher amplitude stimulations. During prolonged stimulation trains, a sub-population of somas fail to maintain calcium activity. Interestingly, neuropil calcium activity is 3-fold less correlated to somatic calcium activity for cells that drop-out during the long stimulation train compared to cells that sustain activity throughout the train. Glutamate release is apparent only within 20 μm of the electrode and is sustained for at least 10s after cessation of the 15 and 20 μA stimulation train, but not lower amplitudes. SIGNIFICANCE These results demonstrate that increasing amplitude can increase the radius and intensity of neural recruitment, but it also alters the temporal response of some neurons. Further, dense glutamate release is highest within the first 20 μm of the electrode site even at high amplitudes, suggesting that there may be spatial limitations to the amplitude parameter space. The glutamate elevation outlasts stimulation, suggesting that high-amplitude stimulation may affect neurotransmitter re-uptake. This ultimately suggests that increasing the amplitude of ICMS device stimulation may fundamentally alter the temporal neural response, which could have implications for using amplitude to improve the ICMS effect or "offset" the effects of glial scarring.
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Affiliation(s)
- James R Eles
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Takashi D Y Kozai
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Center for the Neural Basis of Cognition, University of Pittsburgh, Carnegie Mellon University, Pittsburgh, PA, USA; Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA; NeuroTech Center, University of Pittsburgh Brain Institute, Pittsburgh, PA, USA.
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Hughes C, Herrera A, Gaunt R, Collinger J. Bidirectional brain-computer interfaces. BRAIN-COMPUTER INTERFACES 2020; 168:163-181. [DOI: 10.1016/b978-0-444-63934-9.00013-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Sombeck JT, Miller LE. Short reaction times in response to multi-electrode intracortical microstimulation may provide a basis for rapid movement-related feedback. J Neural Eng 2019; 17:016013. [PMID: 31778982 PMCID: PMC7189902 DOI: 10.1088/1741-2552/ab5cf3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
OBJECTIVE Tetraplegic patients using brain-machine interfaces can make visually guided reaches with robotic arms. However, restoring proprioceptive feedback to these patients will be critical, as evidenced by the movement deficit in patients with proprioceptive loss. Proprioception is critical in large part because it provides faster feedback than vision. Intracortical microstimulation (ICMS) is a promising approach, but the ICMS-evoked reaction time (RT) is typically slower than that to natural proprioceptive and often even visual cues, implying that ICMS feedback may not be fast enough to guide movement. APPROACH For most sensory modalities, RT decreases with increased stimulus intensity. Thus, it may be that stimulation intensities beyond what has previously been used will result in faster RTs. To test this, we compared the RT to ICMS applied through multi-electrode arrays in area 2 of somatosensory cortex to that of mechanical and visual cues. MAIN RESULTS We found that the RT to single-electrode ICMS decreased with increased current, frequency, and train length. For 100 µA, 330 Hz stimulation, the highest single-electrode intensity we tested routinely, most electrodes resulted in RTs slower than the mechanical cue but slightly faster than the visual cue. While increasing the current beyond 100 µA resulted in faster RTs, sustained stimulation at this level may damage tissue. Alternatively, by stimulating through multiple electrodes (mICMS), a large amount of current can be injected while keeping that through each electrode at a safe level. We found that stimulation with at least 480 µA equally distributed over 16 electrodes could produce RTs as much as 20 ms faster than the mechanical cue, roughly the conduction delay to cortex from the periphery. SIGNIFICANCE These results suggest that mICMS may provide a means to supply rapid, movement-related feedback. Future neuroprosthetics may need spatiotemporally patterned mICMS to convey useful somatosensory information. Novelty & Significance Intracortical microstimulation (ICMS) is a promising approach for providing artificial somatosensation to patients with spinal cord injury or limb amputation, but in prior experiments, subjects have been unable to respond as quickly to it as to natural cues. We have investigated the use of multi-electrode stimulation (mICMS) and discovered that it can produce reaction times as fast or faster even than natural mechanical cues. Although our stimulus trains were not modulated in time, this result opens the door to more complex spatiotemporal patterns of mICMS that might be used to rapidly write in complex somatosensory information to the CNS.
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Affiliation(s)
- Joseph T Sombeck
- Department of Physiology, Northwestern University, Chicago, IL, United States of America. Department of Biomedical Engineering, Northwestern University, Evanston, IL, United States of America
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Trevathan JK, Baumgart IW, Nicolai EN, Gosink BA, Asp AJ, Settell ML, Polaconda SR, Malerick KD, Brodnick SK, Zeng W, Knudsen BE, McConico AL, Sanger Z, Lee JH, Aho JM, Suminski AJ, Ross EK, Lujan JL, Weber DJ, Williams JC, Franke M, Ludwig KA, Shoffstall AJ. An Injectable Neural Stimulation Electrode Made from an In-Body Curing Polymer/Metal Composite. Adv Healthc Mater 2019; 8:e1900892. [PMID: 31697052 PMCID: PMC10425988 DOI: 10.1002/adhm.201900892] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 09/20/2019] [Indexed: 12/15/2022]
Abstract
Implanted neural stimulation and recording devices hold vast potential to treat a variety of neurological conditions, but the invasiveness, complexity, and cost of the implantation procedure greatly reduce access to an otherwise promising therapeutic approach. To address this need, a novel electrode that begins as an uncured, flowable prepolymer that can be injected around a neuroanatomical target to minimize surgical manipulation is developed. Referred to as the Injectrode, the electrode conforms to target structures forming an electrically conductive interface which is orders of magnitude less stiff than conventional neuromodulation electrodes. To validate the Injectrode, detailed electrochemical and microscopy characterization of its material properties is performed and the feasibility of using it to stimulate the nervous system electrically in rats and swine is validated. The silicone-metal-particle composite performs very similarly to pure wire of the same metal (silver) in all measures, including exhibiting a favorable cathodic charge storage capacity (CSCC ) and charge injection limits compared to the clinical LivaNova stimulation electrode and silver wire electrodes. By virtue of its simplicity, the Injectrode has the potential to be less invasive, more robust, and more cost-effective than traditional electrode designs, which could increase the adoption of neuromodulation therapies for existing and new indications.
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Affiliation(s)
- James K Trevathan
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, 55902, USA
| | - Ian W Baumgart
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Evan N Nicolai
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, 55902, USA
| | - Brian A Gosink
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Anders J Asp
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, 55902, USA
| | - Megan L Settell
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, 55902, USA
| | - Shyam R Polaconda
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Kevin D Malerick
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Sarah K Brodnick
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Weifeng Zeng
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Bruce E Knudsen
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, 55902, USA
| | - Andrea L McConico
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, 55902, USA
| | - Zachary Sanger
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, 55902, USA
| | - Jannifer H Lee
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, 55902, USA
| | - Johnathon M Aho
- Division of General Thoracic Surgery, Mayo Clinic, Rochester, MN, 55902, USA
- Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, 55902, USA
| | - Aaron J Suminski
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Erika K Ross
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, 55902, USA
| | - Jose L Lujan
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, 55902, USA
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, 55902, USA
- Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, 55902, USA
| | - Douglas J Weber
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Justin C Williams
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | | | - Kip A Ludwig
- Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Neurosurgery, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Neurologic Surgery, Mayo Clinic, Rochester, MN, 55902, USA
- Neuronoff Inc., Valencia, CA, 91354, USA
| | - Andrew J Shoffstall
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA
- Neuronoff Inc., Valencia, CA, 91354, USA
- Advanced Platform Technologies Center, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH, 44106, USA
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Torres-Martinez N, Ratel D, Crétallaz C, Gaude C, Maubert S, Divoux JL, Henry C, Guiraud D, Sauter-Starace F. Reliability of parylene-based multi-electrode arrays chronically implanted in adult rat brains, and evidence of electrical stimulation on contact impedance. J Neural Eng 2019; 16:066047. [PMID: 31374559 DOI: 10.1088/1741-2552/ab3836] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
OBJECTIVE The goal of this study was to evaluate the long-term behavior of the surface electrode through electrochemical characterization and follow-up of implanted parylene/platinum microelectrodes. APPROACH To this aim, we designed and manufactured specific planar electrodes for cortical implantation for a rat model. This work was included in the INTENSE® project, one of the goals of which was to prove the feasibility of selective neural recording or stimulation with cuff electrodes around the vagus nerve. MAIN RESULTS After a 12-week implantation in a rat model, we can report that these microelectrodes have withstood in vivo use. Regarding the biocompatibility of the electrodes (materials and manufacturing process), no adverse effect was reported. Indeed, after the three-month implantation, we characterized limited tissue reaction beneath the electrodes and showed an increase and a stabilization of their impedance. Interestingly, the follow-up of the electrochemical impedance combined with electrical stimulation highlighted a drop in the impedance up to 60% at 1 kHz after ten minutes of electrical stimulation at 110 Hz. SIGNIFICANCE This study gives evidence of the biocompatibility of the parylene platinum contact array designed for the project and confirms the effect of stimulation on the contact impedance.
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36
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Torres-Martinez N, Cretallaz C, Ratel D, Mailley P, Gaude C, Costecalde T, Hebert C, Bergonzo P, Scorsone E, Mazellier JP, Divoux JL, Sauter-Starace F. Evaluation of chronically implanted subdural boron doped diamond/CNT recording electrodes in miniature swine brain. Bioelectrochemistry 2019; 129:79-89. [DOI: 10.1016/j.bioelechem.2019.05.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 05/10/2019] [Accepted: 05/10/2019] [Indexed: 11/29/2022]
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Maeng J, Chakraborty B, Geramifard N, Kang T, Rihani RT, Joshi-Imre A, Cogan SF. High-charge-capacity sputtered iridium oxide neural stimulation electrodes deposited using water vapor as a reactive plasma constituent. J Biomed Mater Res B Appl Biomater 2019; 108:880-891. [PMID: 31353822 DOI: 10.1002/jbm.b.34442] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/06/2019] [Accepted: 06/28/2019] [Indexed: 11/07/2022]
Abstract
The deposition and properties of sputtered iridium oxide films (SIROFs) using water vapor as a reactive gas constituent are investigated for their potential as high-charge-capacity neural stimulation electrodes. Systematic investigation through a series of optical and electrochemical measurements reveals that the incorporation of water vapor as a reactive gas constituent, along with oxygen, alters the reduction-oxidation (redox) state of the plasma as well as its morphology and the electrochemical characteristics, including the cathodal charge-storage capacity (CSCc ) and charge-injection capacity (CIC), of the SIROF. An apparent optimal O2 :H2 O gas ratio of 1:3 produced SIROF with a CSCc of 182.0 mC cm-2 μm-1 (median, Q1 = 172.5, Q3 = 193.4, n = 15) and a CIC of 3.57 mC cm-2 (median, Q1 = 2.97, Q3 = 4.58, n = 12) for 300-nm-thick films. These values are higher than those obtained with SIROFs deposited using no water vapor by a factor of 2.3 and 1.7 for the CSCc and CIC, respectively. Additionally, the SIROF showed minimal changes in electrochemical characteristics over 109 pulses of constant current stimulation and showed no indication of cytotoxicity toward primary cortical neurons in a cell viability assay. These results warrant investigation of the chronic recording and stimulation capabilities of the SIROF for implantable microelectrode arrays.
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Affiliation(s)
- Jimin Maeng
- Department of Bioengineering, University of Texas at Dallas, Richardson, Texas
| | - Bitan Chakraborty
- Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas
| | - Negar Geramifard
- Department of Bioengineering, University of Texas at Dallas, Richardson, Texas
| | - Tong Kang
- Department of Mechanical Engineering, University of Texas at Dallas, Richardson, Texas
| | - Rashed T Rihani
- Department of Bioengineering, University of Texas at Dallas, Richardson, Texas
| | - Alexandra Joshi-Imre
- Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas
| | - Stuart F Cogan
- Department of Bioengineering, University of Texas at Dallas, Richardson, Texas
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Wellman SM, Li L, Yaxiaer Y, McNamara I, Kozai TDY. Revealing Spatial and Temporal Patterns of Cell Death, Glial Proliferation, and Blood-Brain Barrier Dysfunction Around Implanted Intracortical Neural Interfaces. Front Neurosci 2019; 13:493. [PMID: 31191216 PMCID: PMC6546924 DOI: 10.3389/fnins.2019.00493] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 04/29/2019] [Indexed: 12/11/2022] Open
Abstract
Improving the long-term performance of neural electrode interfaces requires overcoming severe biological reactions such as neuronal cell death, glial cell activation, and vascular damage in the presence of implanted intracortical devices. Past studies traditionally observe neurons, microglia, astrocytes, and blood-brain barrier (BBB) disruption around inserted microelectrode arrays. However, analysis of these factors alone yields poor correlation between tissue inflammation and device performance. Additionally, these studies often overlook significant biological responses that can occur during acute implantation injury. The current study employs additional histological markers that provide novel information about neglected tissue components-oligodendrocytes and their myelin structures, oligodendrocyte precursor cells, and BBB -associated pericytes-during the foreign body response to inserted devices at 1, 3, 7, and 28 days post-insertion. Our results reveal unique temporal and spatial patterns of neuronal and oligodendrocyte cell loss, axonal and myelin reorganization, glial cell reactivity, and pericyte deficiency both acutely and chronically around implanted devices. Furthermore, probing for immunohistochemical markers that highlight mechanisms of cell death or patterns of proliferation and differentiation have provided new insight into inflammatory tissue dynamics around implanted intracortical electrode arrays.
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Affiliation(s)
- Steven M. Wellman
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
- Center for the Neural Basis of Cognition, Pittsburgh, PA, United States
| | - Lehong Li
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Yalikun Yaxiaer
- Eberly College of Science, Pennsylvania State University, University Park, PA, United States
| | - Ingrid McNamara
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Takashi D. Y. Kozai
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
- Center for the Neural Basis of Cognition, Pittsburgh, PA, United States
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States
- McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, United States
- NeuroTech Center, University of Pittsburgh Brain Institute, Pittsburgh, PA, United States
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39
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Nambiar A, Nolta NF, Han M. 3D Reconstruction of the Intracortical Volume Around a Hybrid Microelectrode Array. Front Neurosci 2019; 13:393. [PMID: 31068786 PMCID: PMC6491727 DOI: 10.3389/fnins.2019.00393] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 04/05/2019] [Indexed: 11/17/2022] Open
Abstract
Extensive research using penetrating electrodes implanted in the central and peripheral nervous systems has been performed for many decades with significant advances made in recent years. While penetrating devices provide proximity to individual neurons in vivo, they suffer from declining performance over the course of months and often fail within a year. 2D histology studies using serial tissue sections have been extremely insightful in identifying and quantifying factors such as astroglial scar formation and neuronal death around the implant sites that may be contributing to failures. However, 2D histology has limitations in providing a holistic picture of the problems occurring at the electrode-tissue interface and struggles to analyze tissue below the electrode tips where the electrode tracks are no longer visible. In this study, we present 3D reconstruction of serial sections to overcome the limitations of 2D histological analysis. We used a cohort of software: XuvStitch, AutoAligner, and Imaris coupled with custom MATLAB programming to correct warping effects. Once the 3D image volume was reconstructed, we were able to use Imaris to quantify neuronal densities around the electrode tips of a hybrid microelectrode array incorporating Blackrock, Microprobes, and NeuroNexus electrodes in the same implant. This paper presents proof-of-concept and detailed methodological description of a technique which can be used to quantify neuronal densities in future studies of implanted electrodes.
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Affiliation(s)
- Aparna Nambiar
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT, United States
| | - Nicholas F Nolta
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT, United States
| | - Martin Han
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT, United States
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40
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Cramer SD, Lee JS, Butt MT, Paulin J, Stoffregen WC. Neurologic Medical Device Overview for Pathologists. Toxicol Pathol 2019; 47:250-263. [PMID: 30599801 DOI: 10.1177/0192623318816685] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Thorough morphologic evaluations of medical devices placed in or near the nervous system depend on many factors. Pathologists interpreting a neurologic device study must be familiar with the regulatory framework affecting device development, biocompatibility and safety determinants impacting nervous tissue responses, and appropriate study design, including the use of appropriate animal models, group design, device localization, euthanasia time points, tissue examination, sampling and processing, histochemistry and immunohistochemistry, and reporting. This overview contextualizes these features of neurologic medical devices for pathologists engaged in device evaluations.
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Affiliation(s)
| | | | - Mark T Butt
- 1 Tox Path Specialists, LLC, Frederick, Maryland, USA
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41
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Michelson NJ, Eles JR, Vazquez AL, Ludwig KA, Kozai TDY. Calcium activation of cortical neurons by continuous electrical stimulation: Frequency dependence, temporal fidelity, and activation density. J Neurosci Res 2018; 97:620-638. [PMID: 30585651 DOI: 10.1002/jnr.24370] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 11/20/2018] [Accepted: 11/28/2018] [Indexed: 01/18/2023]
Abstract
Electrical stimulation of the brain has become a mainstay of fundamental neuroscience research and an increasingly prevalent clinical therapy. Despite decades of use in basic neuroscience research and the growing prevalence of neuromodulation therapies, gaps in knowledge regarding activation or inactivation of neural elements over time have limited its ability to adequately interpret evoked downstream responses or fine-tune stimulation parameters to focus on desired responses. In this work, in vivo two-photon microscopy was used to image neuronal calcium activity in layer 2/3 neurons of somatosensory cortex (S1) in male C57BL/6J-Tg(Thy1-GCaMP6s)GP4.3Dkim/J mice during 30 s of continuous electrical stimulation at varying frequencies. We show frequency-dependent differences in spatial and temporal somatic responses during continuous stimulation. Our results elucidate conflicting results from prior studies reporting either dense spherical activation of somas biased toward those near the electrode, or sparse activation of somas at a distance via axons near the electrode. These findings indicate that the neural element specific temporal response local to the stimulating electrode changes as a function of applied charge density and frequency. These temporal responses need to be considered to properly interpret downstream circuit responses or determining mechanisms of action in basic science experiments or clinical therapeutic applications.
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Affiliation(s)
- Nicholas J Michelson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Psychiatry, University of British Columbia, Vancouver, British Columbia, Canada
| | - James R Eles
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania.,Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Alberto L Vazquez
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania.,Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania.,Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Kip A Ludwig
- Department of Biomedical Engineering, University of Wisconsin Madison, Madison, Wisconsin.,Department of Neurological Surgery, University of Wisconsin Madison, Madison, Wisconsin
| | - Takashi D Y Kozai
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania.,Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania.,Center for Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania.,McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.,NeuroTech Center, University of Pittsburgh Brain Institute, Pittsburgh, Pennsylvania
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42
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Woods V, Trumpis M, Bent B, Palopoli-Trojani K, Chiang CH, Wang C, Yu C, Insanally MN, Froemke RC, Viventi J. Long-term recording reliability of liquid crystal polymer µECoG arrays. J Neural Eng 2018; 15:066024. [PMID: 30246690 PMCID: PMC6342453 DOI: 10.1088/1741-2552/aae39d] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The clinical use of microsignals recorded over broad cortical regions is largely limited by the chronic reliability of the implanted interfaces. APPROACH We evaluated the chronic reliability of novel 61-channel micro-electrocorticographic (µECoG) arrays in rats chronically implanted for over one year and using accelerated aging. Devices were encapsulated with polyimide (PI) or liquid crystal polymer (LCP), and fabricated using commercial manufacturing processes. In vitro failure modes and predicted lifetimes were determined from accelerated soak testing. Successful designs were implanted epidurally over the rodent auditory cortex. Trends in baseline signal level, evoked responses and decoding performance were reported for over one year of implantation. MAIN RESULTS Devices fabricated with LCP consistently had longer in vitro lifetimes than PI encapsulation. Our accelerated aging results predicted device integrity beyond 3.4 years. Five implanted arrays showed stable performance over the entire implantation period (247-435 d). Our regression analysis showed that impedance predicted signal quality and information content only in the first 31 d of recordings and had little predictive value in the chronic phase (>31 d). In the chronic phase, site impedances slightly decreased yet decoding performance became statistically uncorrelated with impedance. We also employed an improved statistical model of spatial variation to measure sensitivity to locally varying fields, which is typically concealed in standard signal power calculations. SIGNIFICANCE These findings show that µECoG arrays can reliably perform in chronic applications in vivo for over one year, which facilitates the development of a high-density, clinically viable interface.
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Affiliation(s)
- Virginia Woods
- Department of Biomedical Engineering, Duke University, Durham, NC, United States of America
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43
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Tarnaud T, Tanghe E, Haesler S, Lopez CM, Martens L, Joseph W. Investigation of the Stimulation Capabilities of a High-Resolution Neurorecording Probe for the Application of Closed-Loop Deep Brain Stimulation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2018; 2018:2166-2169. [PMID: 30440833 DOI: 10.1109/embc.2018.8512650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Deep brain stimulation is an established surgical treatment for several neurological and movement disorders, such as Parkinson's disease, in which electrostimulation is applied to targeted deep nuclei in the basal ganglia through implanted electrode leads. Recent technological improvements in the field have focused on the theoretical advantage of current steering and adaptive (closed-loop) deep brain stimulation. Current steering between several active electrodes would allow for improved accuracy when targeting the desired brain structures. This has the additional benefit of avoiding undesired stimulation of neural tracts that are related to side effects, e.g., internal capsule fibres of passage in subthalamic nucleus deep brain stimulation. Closed-loop deep brain stimulation is based on the premise of continuous recording of a proxy for pathological neural activity (such as beta-band power of measured local field potentials in patients with Parkinson's disease) and accordingly adapting the used stimulus parameters. In this study, we investigate the suitability of an existing highresolution neurorecording probe for high-precision neurostimulation. If a subset of the probe's recording electrodes can be used for stimulation, then the probe would be a suitable candidate for closed-loop deep brain stimulation. A finiteelement model is used to calculate the electric potential, induced by current injection through the high-resolution probe, for different sets of active electrodes. Volumes of activated tissue are calculated and a comparison is made between the highresolution probe and a conventional stimulation lead. We investigate the capability of the probe to shift the volume of activated tissue by steering currents to different sets of active electrodes. Finally, safety limits for the injected current are used to determine the size of the volume in which neurons can be activated with the relatively small electrodes patches on the highresolution probe.
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44
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Zhang Z, Klausen LH, Chen M, Dong M. Electroactive Scaffolds for Neurogenesis and Myogenesis: Graphene-Based Nanomaterials. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1801983. [PMID: 30264534 DOI: 10.1002/smll.201801983] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 07/28/2018] [Indexed: 05/24/2023]
Abstract
One of the major issues in tissue engineering is constructing a functional scaffold to support cell growth and also provide proper synergistic guidance cues. Graphene-based nanomaterials have emerged as biocompatible and electroactive scaffolds for neurogenesis and myogenesis, due to their excellent tunable chemical, physical, and mechanical properties. This review first assesses the recent investigations focusing on the fabrication and applications of graphene-based nanomaterials for neurogenesis and myogenesis, in the form of either 2D films, 3D scaffolds, or composite architectures. Besides, because of their outstanding electrical properties, graphene family materials are particularly suitable for designing electroactive scaffolds that could provide proper electrical stimulation (i.e., electrical or photo stimuli) to promote the regeneration of excitable neurons and muscle cells. Therefore, the effects and mechanism of electrical and/or photo stimulations on neurogenesis and myogenesis are followed. Furthermore, studies on their biocompatibilities and toxicities especially to neural and muscle cells are evaluated. Finally, the future challenges and perspectives in facilitating the development of clinical translation of graphene-family nanomaterials in treating neurodegenerative and muscle diseases are discussed.
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Affiliation(s)
- Zhongyang Zhang
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000, Aarhus C, Denmark
| | | | - Menglin Chen
- Department of Engineering, Aarhus University, DK-8000, Aarhus C, Denmark
| | - Mingdong Dong
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000, Aarhus C, Denmark
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
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45
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Shepherd RK, Villalobos J, Burns O, Nayagam DAX. The development of neural stimulators: a review of preclinical safety and efficacy studies. J Neural Eng 2018; 15:041004. [PMID: 29756600 PMCID: PMC6049833 DOI: 10.1088/1741-2552/aac43c] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Given the rapid expansion of the field of neural stimulation and the rigorous regulatory approval requirements required before these devices can be applied clinically, it is important that there is clarity around conducting preclinical safety and efficacy studies required for the development of this technology. APPROACH The present review examines basic design principles associated with the development of a safe neural stimulator and describes the suite of preclinical safety studies that need to be considered when taking a device to clinical trial. MAIN RESULTS Neural stimulators are active implantable devices that provide therapeutic intervention, sensory feedback or improved motor control via electrical stimulation of neural or neuro-muscular tissue in response to trauma or disease. Because of their complexity, regulatory bodies classify these devices in the highest risk category (Class III), and they are therefore required to go through a rigorous regulatory approval process before progressing to market. The successful development of these devices is achieved through close collaboration across disciplines including engineers, scientists and a surgical/clinical team, and the adherence to clear design principles. Preclinical studies form one of several key components in the development pathway from concept to product release of neural stimulators. Importantly, these studies provide iterative feedback in order to optimise the final design of the device. Key components of any preclinical evaluation include: in vitro studies that are focussed on device reliability and include accelerated testing under highly controlled environments; in vivo studies using animal models of the disease or injury in order to assess efficacy and, given an appropriate animal model, the safety of the technology under both passive and electrically active conditions; and human cadaver and ex vivo studies designed to ensure the device's form factor conforms to human anatomy, to optimise the surgical approach and to develop any specialist surgical tooling required. SIGNIFICANCE The pipeline from concept to commercialisation of these devices is long and expensive; careful attention to both device design and its preclinical evaluation will have significant impact on the duration and cost associated with taking a device through to commercialisation. Carefully controlled in vitro and in vivo studies together with ex vivo and human cadaver trials are key components of a thorough preclinical evaluation of any new neural stimulator.
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Affiliation(s)
- Robert K Shepherd
- Bionics Institute, East Melbourne, Australia. Medical Bionics Department, University of Melbourne, Melbourne, Australia
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46
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47
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Ghafoor U, Kim S, Hong KS. Selectivity and Longevity of Peripheral-Nerve and Machine Interfaces: A Review. Front Neurorobot 2017; 11:59. [PMID: 29163122 PMCID: PMC5671609 DOI: 10.3389/fnbot.2017.00059] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Accepted: 10/17/2017] [Indexed: 11/22/2022] Open
Abstract
For those individuals with upper-extremity amputation, a daily normal living activity is no longer possible or it requires additional effort and time. With the aim of restoring their sensory and motor functions, theoretical and technological investigations have been carried out in the field of neuroprosthetic systems. For transmission of sensory feedback, several interfacing modalities including indirect (non-invasive), direct-to-peripheral-nerve (invasive), and cortical stimulation have been applied. Peripheral nerve interfaces demonstrate an edge over the cortical interfaces due to the sensitivity in attaining cortical brain signals. The peripheral nerve interfaces are highly dependent on interface designs and are required to be biocompatible with the nerves to achieve prolonged stability and longevity. Another criterion is the selection of nerves that allows minimal invasiveness and damages as well as high selectivity for a large number of nerve fascicles. In this paper, we review the nerve-machine interface modalities noted above with more focus on peripheral nerve interfaces, which are responsible for provision of sensory feedback. The invasive interfaces for recording and stimulation of electro-neurographic signals include intra-fascicular, regenerative-type interfaces that provide multiple contact channels to a group of axons inside the nerve and the extra-neural-cuff-type interfaces that enable interaction with many axons around the periphery of the nerve. Section Current Prosthetic Technology summarizes the advancements made to date in the field of neuroprosthetics toward the achievement of a bidirectional nerve-machine interface with more focus on sensory feedback. In the Discussion section, the authors propose a hybrid interface technique for achieving better selectivity and long-term stability using the available nerve interfacing techniques.
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Affiliation(s)
- Usman Ghafoor
- School of Mechanical Engineering, Pusan National University, Busan, South Korea
| | - Sohee Kim
- Department of Robotics Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea
| | - Keum-Shik Hong
- School of Mechanical Engineering, Pusan National University, Busan, South Korea.,Department of Cogno-Mechatronics Engineering, Pusan National University, Busan, South Korea
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48
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Sorgini F, Caliò R, Carrozza MC, Oddo CM. Haptic-assistive technologies for audition and vision sensory disabilities. Disabil Rehabil Assist Technol 2017; 13:394-421. [DOI: 10.1080/17483107.2017.1385100] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Francesca Sorgini
- The BioRobotics Institute, Scuola Superiore Sant’Anna, Pontedera, Pisa, Italy
| | - Renato Caliò
- The BioRobotics Institute, Scuola Superiore Sant’Anna, Pontedera, Pisa, Italy
| | | | - Calogero Maria Oddo
- The BioRobotics Institute, Scuola Superiore Sant’Anna, Pontedera, Pisa, Italy
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49
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Lee SW, Fried SI. Enhanced Control of Cortical Pyramidal Neurons With Micromagnetic Stimulation. IEEE Trans Neural Syst Rehabil Eng 2017; 25:1375-1386. [PMID: 27893396 PMCID: PMC5498237 DOI: 10.1109/tnsre.2016.2631446] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Magnetic stimulation is less sensitive to the inflammatory reactions that plague conventional electrode-based cortical implants and therefore may be useful as a next-generation (implanted) cortical prosthetic. The fields arising from micro-coils are quite small however and thus, their ability to modulate cortical activity must first be established. Here, we show that layer V pyramidal neurons (PNs) can be strongly activated by micro-coil stimulation and further, the asymmetric fields arising from such coils do not simultaneously activate horizontally-oriented axon fibers, thus confining activation to a focal region around the coil. The spatially-narrow fields from micro-coils allowed the sensitivity of different regions within a single PN to be compared: while the proximal axon was most sensitive in naïve cells, repetitive stimulation over the apical dendrite led to a change in state of the neuron that reduced thresholds there to below those of the axon. Thus, our results raise the possibility that regardless of the mode of stimulation, penetration depths that target specific portions of the apical dendrite may actually be more effective than those that target Layer 6. Interestingly, the state change had similar properties to state changes described previously at the systems level, suggesting a possible neuronal mechanism underlying such responses.
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50
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Wilks SJ, Hara SA, Ross EK, Nicolai EN, Pignato PA, Cates AW, Ludwig KA. Non-clinical and Pre-clinical Testing to Demonstrate Safety of the Barostim Neo Electrode for Activation of Carotid Baroreceptors in Chronic Human Implants. Front Neurosci 2017; 11:438. [PMID: 28824361 PMCID: PMC5539240 DOI: 10.3389/fnins.2017.00438] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 07/17/2017] [Indexed: 11/28/2022] Open
Abstract
The Barostim neo™ electrode was developed by CVRx, Inc.to deliver baroreflex activation therapy (BAT)™ to treat hypertension and heart failure. The neo electrode concept was designed to deliver electrical stimulation to the baroreceptors within the carotid sinus bulb, while minimizing invasiveness of the implant procedure. This device is currently CE marked in Europe, and in a Pivotal (akin to Phase III) Trial in the United States. Here we present the in vitro and in vivo safety testing that was completed in order to obtain necessary regulatory approval prior to conducting human studies in Europe, as well as an FDA Investigational Device Exemption (IDE) to conduct a Pivotal Trial in the United States. Stimulated electrodes (10 mA, 500 μs, 100 Hz) were compared to unstimulated electrodes using optical microscopy and several electrochemical techniques over the course of 27 weeks. Electrode dissolution was evaluated by analyzing trace metal content of solutions in which electrodes were stimulated. Lastly, safety testing under Good Laboratory Practice guidelines was conducted in an ovine animal model over a 12 and 24 week time period, with results processed and evaluated by an independent histopathologist. Long-term stimulation testing indicated that the neo electrode with a sputtered iridium oxide coating can be stimulated at maximal levels for the lifetime of the implant without clinically significant dissolution of platinum or iridium, and without increasing the potential at the electrode interface to cause hydrolysis or significant tissue damage. Histological examination of tissue that was adjacent to the neo electrodes indicated no clinically significant signs of increased inflammation and no arterial stenosis as a result of 6 months of continuous stimulation. The work presented here involved rigorous characterization and evaluation testing of the neo electrode, which was used to support its safety for chronic implantation. The testing strategies discussed provide a starting point and proven framework for testing new neuromodulation electrode concepts to support regulatory approval for clinical studies.
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Affiliation(s)
| | - Seth A Hara
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States
| | - Erika K Ross
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States
| | - Evan N Nicolai
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States
| | | | | | - Kip A Ludwig
- Department of Neurologic Surgery, Mayo ClinicRochester, MN, United States
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