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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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52
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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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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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Lee SW, Fallegger F, Casse BDF, Fried SI. Implantable microcoils for intracortical magnetic stimulation. SCIENCE ADVANCES 2016; 2:e1600889. [PMID: 27957537 PMCID: PMC5148213 DOI: 10.1126/sciadv.1600889] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 11/03/2016] [Indexed: 05/20/2023]
Abstract
Neural prostheses that stimulate the neocortex have the potential to treat a wide range of neurological disorders. However, the efficacy of electrode-based implants remains limited, with persistent challenges that include an inability to create precise patterns of neural activity as well as difficulties in maintaining response consistency over time. These problems arise from fundamental limitations of electrodes as well as their susceptibility to implantation and have proven difficult to overcome. Magnetic stimulation can address many of these limitations, but coils small enough to be implanted into the cortex were not thought strong enough to activate neurons. We describe a new microcoil design and demonstrate its effectiveness for both activating cortical neurons and driving behavioral responses. The stimulation of cortical pyramidal neurons in brain slices in vitro was reliable and could be confined to spatially narrow regions (<60 μm). The spatially asymmetric fields arising from the coil helped to avoid the simultaneous activation of passing axons. In vivo implantation was safe and resulted in consistent and predictable behavioral responses. The high permeability of magnetic fields to biological substances may yield another important advantage because it suggests that encapsulation and other adverse effects of implantation will not diminish coil performance over time, as happens to electrodes. These findings suggest that a coil-based implant might be a useful alternative to existing electrode-based devices. The enhanced selectivity of microcoil-based magnetic stimulation will be especially useful for visual prostheses as well as for many brain-computer interface applications that require precise activation of the cortex.
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Affiliation(s)
- Seung Woo Lee
- Boston Veterans Affairs Healthcare System, Boston, MA 02130, USA
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Florian Fallegger
- Palo Alto Research Center, a Xerox company, Palo Alto, CA 94304, USA
| | | | - Shelley I. Fried
- Boston Veterans Affairs Healthcare System, Boston, MA 02130, USA
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
- Corresponding author.
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55
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Delhaye BP, Saal HP, Bensmaia SJ. Key considerations in designing a somatosensory neuroprosthesis. ACTA ACUST UNITED AC 2016; 110:402-408. [PMID: 27815182 DOI: 10.1016/j.jphysparis.2016.11.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Revised: 10/20/2016] [Accepted: 11/01/2016] [Indexed: 12/22/2022]
Abstract
In recent years, a consensus has emerged that somatosensory feedback needs to be provided for upper limb neuroprostheses to be useful. An increasingly promising approach to sensory restoration is to electrically stimulate neurons along the somatosensory neuraxis to convey information about the state of the prosthetic limb and about contact with objects. To date, efforts toward artificial sensory feedback have consisted mainly of demonstrating that some sensory information could be conveyed using a small number of stimulation patterns, generally delivered through single electrodes. However impressive these achievements are, results from different studies are hard to compare, as each research team implements different stimulation patterns and tests the elicited sensations differently. A critical question is whether different stimulation strategies will generalize from contrived laboratory settings to activities of daily living. Here, we lay out some key specifications that an artificial somatosensory channel should meet, discuss how different approaches should be evaluated, and caution about looming challenges that the field of sensory restoration will face.
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Affiliation(s)
- Benoit P Delhaye
- Department of Organismal Biology and Anatomy, University of Chicago, United States
| | - Hannes P Saal
- Department of Organismal Biology and Anatomy, University of Chicago, United States
| | - Sliman J Bensmaia
- Department of Organismal Biology and Anatomy, University of Chicago, United States.
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56
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Flesher SN, Collinger JL, Foldes ST, Weiss JM, Downey JE, Tyler-Kabara EC, Bensmaia SJ, Schwartz AB, Boninger ML, Gaunt RA. Intracortical microstimulation of human somatosensory cortex. Sci Transl Med 2016; 8:361ra141. [PMID: 27738096 DOI: 10.1126/scitranslmed.aaf8083] [Citation(s) in RCA: 396] [Impact Index Per Article: 49.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 10/05/2016] [Indexed: 12/21/2022]
Abstract
Intracortical microstimulation of the somatosensory cortex offers the potential for creating a sensory neuroprosthesis to restore tactile sensation. Whereas animal studies have suggested that both cutaneous and proprioceptive percepts can be evoked using this approach, the perceptual quality of the stimuli cannot be measured in these experiments. We show that microstimulation within the hand area of the somatosensory cortex of a person with long-term spinal cord injury evokes tactile sensations perceived as originating from locations on the hand and that cortical stimulation sites are organized according to expected somatotopic principles. Many of these percepts exhibit naturalistic characteristics (including feelings of pressure), can be evoked at low stimulation amplitudes, and remain stable for months. Further, modulating the stimulus amplitude grades the perceptual intensity of the stimuli, suggesting that intracortical microstimulation could be used to convey information about the contact location and pressure necessary to perform dexterous hand movements associated with object manipulation.
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Affiliation(s)
- Sharlene N Flesher
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jennifer L Collinger
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Center for the Neural Basis of Cognition, Pittsburgh, PA 15213, USA.,Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Department of Veterans Affairs Medical Center, Pittsburgh, PA 15206, USA
| | - Stephen T Foldes
- Center for the Neural Basis of Cognition, Pittsburgh, PA 15213, USA.,Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Department of Veterans Affairs Medical Center, Pittsburgh, PA 15206, USA
| | - Jeffrey M Weiss
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - John E Downey
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Center for the Neural Basis of Cognition, Pittsburgh, PA 15213, USA
| | - Elizabeth C Tyler-Kabara
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA 15213, USA.,McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Sliman J Bensmaia
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA
| | - Andrew B Schwartz
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Center for the Neural Basis of Cognition, Pittsburgh, PA 15213, USA.,McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA.,Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Systems Neuroscience Institute, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Michael L Boninger
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA 15213, USA.,Department of Veterans Affairs Medical Center, Pittsburgh, PA 15206, USA.,McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Robert A Gaunt
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA. .,Center for the Neural Basis of Cognition, Pittsburgh, PA 15213, USA.,Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA 15213, USA
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57
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Nguyen HT, Tangutooru SM, Rountree CM, Kantzos AJK, Tarlochan F, Yoon WJ, Troy JB. Thalamic Visual Prosthesis. IEEE Trans Biomed Eng 2016; 63:1573-80. [DOI: 10.1109/tbme.2016.2567300] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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North JM, Hong KSJ, Cho PY. Clinical Outcomes of 1 kHz Subperception Spinal Cord Stimulation in Implanted Patients With Failed Paresthesia-Based Stimulation: Results of a Prospective Randomized Controlled Trial. Neuromodulation 2016; 19:731-737. [PMID: 27186822 DOI: 10.1111/ner.12441] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 02/25/2016] [Accepted: 03/16/2016] [Indexed: 12/01/2022]
Abstract
BACKGROUND Pain relief via spinal cord stimulation (SCS) has historically revolved around producing paresthesia to replace pain, with success measured by the extent of paresthesia-pain overlap. In a recent murine study, by Shechter et al., showed the superior efficacy of high frequency SCS (1 kHz and 10 kHz) at inhibiting the effects of mechanical hypersensitivity compared to sham or 50 Hz stimulation. In the same study, authors report there were no differences in efficacy between 1 kHz and 10 kHz delivered at subperception stimulation strength (80% of motor threshold). Therefore, we designed a randomized, 2 × 2 crossover study of low frequency supra-perception SCS vs. subperception SCS at 1 kHz frequency in order to test whether subperception stimulation at 1 kHz was sufficient to provide effective pain relief in human subjects. METHODS Twenty-two subjects with SCS, and inadequate pain relief based on numeric pain rating scale (NPRS) scores (>5) were enrolled, and observed for total of seven weeks (three weeks of treatment, one week wash off, and another three weeks of treatment). Subjects were asked to rate their pain on NPRS as a primary efficacy variable, and complete the Oswestry Disability Index (ODI) and Patient's Global Impression of Change (PGIC) as secondary outcome measures. RESULTS Out of 22 subjects that completed the study, 21 subjects (95%) reported improvements in average, best, and worst pain NPRS scores. All NPRS scores were significantly lower with subperception stimulation compared to paresthesia-based stimulation (p < 0.01, p < 0.05, and p < 0.05, respectively). As with NPRS scores, the treatment effect of subperception stimulation was significantly greater than that of paresthesia based stimulation on ODI scores (p = 3.9737 × 10-5 ) and PGIC scores (p = 3.0396 × 10-5 ).
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Affiliation(s)
- James M North
- The Center for Clinical Research, Carolinas Pain Institute, Winston-Salem, NC, USA
| | - Kyung-Soo Jason Hong
- The Center for Clinical Research, Carolinas Pain Institute, Winston-Salem, NC, USA.
| | - Philip Young Cho
- Mathematical Sciences, United States Air Force Academy, Colorado Springs, CO, USA
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Christie BP, Ashmont KR, House PA, Greger B. Approaches to a cortical vision prosthesis: implications of electrode size and placement. J Neural Eng 2016; 13:025003. [PMID: 26905379 DOI: 10.1088/1741-2560/13/2/025003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE In order to move forward with the development of a cortical vision prosthesis, the critical issues in the field must be identified. APPROACH To begin this process, we performed a brief review of several different cortical and retinal stimulation techniques that can be used to restore vision. MAIN RESULTS Intracortical microelectrodes and epicortical macroelectrodes have been evaluated as the basis of a vision prosthesis. We concluded that an important knowledge gap necessitates an experimental in vivo performance evaluation of microelectrodes placed on the surface of the visual cortex. A comparison of the level of vision restored by intracortical versus epicortical microstimulation is necessary. Because foveal representation in the primary visual cortex involves more cortical columns per degree of visual field than does peripheral vision, restoration of foveal vision may require a large number of closely spaced microelectrodes. Based on previous studies of epicortical macrostimulation, it is possible that stimulation via surface microelectrodes could produce a lower spatial resolution, making them better suited for restoring peripheral vision. SIGNIFICANCE The validation of epicortical microstimulation in addition to the comparison of epicortical and intracortical approaches for vision restoration will fill an important knowledge gap and may have important implications for surgical strategies and device longevity. It is possible that the best approach to vision restoration will utilize both epicortical and intracortical microstimulation approaches, applying them appropriately to different visual representations in the primary visual cortex.
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Affiliation(s)
- Breanne P Christie
- School of Biological and Health Systems Engineering, Arizona State University, Tempe AZ, USA
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60
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Cogan SF, Ludwig KA, Welle CG, Takmakov P. Tissue damage thresholds during therapeutic electrical stimulation. J Neural Eng 2016; 13:021001. [PMID: 26792176 DOI: 10.1088/1741-2560/13/2/021001] [Citation(s) in RCA: 198] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Recent initiatives in bioelectronic modulation of the nervous system by the NIH (SPARC), DARPA (ElectRx, SUBNETS) and the GlaxoSmithKline Bioelectronic Medicines effort are ushering in a new era of therapeutic electrical stimulation. These novel therapies are prompting a re-evaluation of established electrical thresholds for stimulation-induced tissue damage. APPROACH In this review, we explore what is known and unknown in published literature regarding tissue damage from electrical stimulation. MAIN RESULTS For macroelectrodes, the potential for tissue damage is often assessed by comparing the intensity of stimulation, characterized by the charge density and charge per phase of a stimulus pulse, with a damage threshold identified through histological evidence from in vivo experiments as described by the Shannon equation. While the Shannon equation has proved useful in assessing the likely occurrence of tissue damage, the analysis is limited by the experimental parameters of the original studies. Tissue damage is influenced by factors not explicitly incorporated into the Shannon equation, including pulse frequency, duty cycle, current density, and electrode size. Microelectrodes in particular do not follow the charge per phase and charge density co-dependence reflected in the Shannon equation. The relevance of these factors to tissue damage is framed in the context of available reports from modeling and in vivo studies. SIGNIFICANCE It is apparent that emerging applications, especially with microelectrodes, will require clinical charge densities that exceed traditional damage thresholds. Experimental data show that stimulation at higher charge densities can be achieved without causing tissue damage, suggesting that safety parameters for microelectrodes might be distinct from those defined for macroelectrodes. However, these increased charge densities may need to be justified by bench, non-clinical or clinical testing to provide evidence of device safety.
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Affiliation(s)
- Stuart F Cogan
- The Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, USA
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61
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Watson M, Dancause N, Sawan M. Intracortical Microstimulation Parameters Dictate the Amplitude and Latency of Evoked Responses. Brain Stimul 2015; 9:276-84. [PMID: 26633857 DOI: 10.1016/j.brs.2015.10.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 10/04/2015] [Accepted: 10/23/2015] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Microstimulation of brain tissue plays a key role in a variety of sensory prosthetics, clinical therapies and research applications. However, the effects of stimulation parameters on the responses they evoke remain widely unknown. OBJECTIVE We aimed to investigate the contribution of each stimulation parameter to the response and identify interactions existing between parameters. METHODS Parameters of the constant-current, biphasic square waveform were examined in acute terminal experiments under ketamine anaesthesia. The motor cortex of 7 Sprague-Dawley rats was stimulated while recording motor evoked potentials (MEP) from the forelimb. Intracortical microstimulation (ICMS) parameters were systematically tested in a pair-wise fashion to observe the influence of each parameter on the amplitude and latency of the MEP. RESULTS The amplitude of the MEP increased continually with stimulus amplitude (p < 0.001) and pulse duration (p = 0.001) throughout the range tested. Increases were also observed when stimuli were raised from low to moderate values of frequency (p = 0.022) and train duration (p = 0.045), after which no further excitation occurs. The latency of MEP initiation decreased when stimulus amplitude (p = 0.037) and frequency (p = 0.001) were raised from low to moderate values, after which the responses plateaued. MEP latencies were further reduced by increasing the pulse duration (p = 0.011), but train duration had no effect. CONCLUSIONS Our data indicate that MEP amplitude and onset latency can be modulated by alterations to a number of stimulus parameters, even in restrictive paradigms, and suggest that the parameters of the standard ICMS signal used for evoking movements from the motor cortex can be further optimized.
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Affiliation(s)
- Meghan Watson
- Polystim Neurotechnologies, Institute of Biomedical Engineering, Polytechnique, Montreal, Quebec, Canada; Département de Neurosciences, Faculté de Médecine, Université de Montréal, Montreal, Quebec, Canada.
| | - Numa Dancause
- Département de Neurosciences, Faculté de Médecine, Université de Montréal, Montreal, Quebec, Canada
| | - Mohamad Sawan
- Polystim Neurotechnologies, Institute of Biomedical Engineering, Polytechnique, Montreal, Quebec, Canada
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Rajan AT, Boback JL, Dammann JF, Tenore FV, Wester BA, Otto KJ, Gaunt RA, Bensmaia SJ. The effects of chronic intracortical microstimulation on neural tissue and fine motor behavior. J Neural Eng 2015; 12:066018. [PMID: 26479701 PMCID: PMC8129590 DOI: 10.1088/1741-2560/12/6/066018] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Objective. One approach to conveying sensory feedback in neuroprostheses is to electrically stimulate sensory neurons in the cortex. For this approach to be viable, it is critical that intracortical microstimulation (ICMS) causes minimal damage to the brain. Here, we investigate the effects of chronic ICMS on the neuronal tissue across a variety of stimulation regimes in non-human primates. We also examine each animal’s ability to use their hand—the cortical representation of which is targeted by the ICMS—as a further assay of possible neuronal damage. Approach. We implanted electrode arrays in the primary somatosensory cortex of three Rhesus macaques and delivered ICMS four hours per day, five days per week, for six months. Multiple regimes of ICMS were delivered to investigate the effects of stimulation parameters on the tissue and behavior. Parameters included current amplitude (10–100 μA), pulse train duration (1, 5 s), and duty cycle (1/1, 1/3). We then performed a range of histopathological assays on tissue near the tips of both stimulated and unstimulated electrodes to assess the effects of chronic ICMS on the tissue and their dependence on stimulation parameters. Main results. While the implantation and residence of the arrays in the cortical tissue did cause significant damage, chronic ICMS had no detectable additional effect; furthermore, the animals exhibited no impairments in fine motor control. Significance. Chronic ICMS may be a viable means to convey sensory feedback in neuroprostheses as it does not cause significant damage to the stimulated tissue.
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Affiliation(s)
- Alexander T Rajan
- Committee on Computational Neuroscience, University of Chicago, Chicago, IL, USA. Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA
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Callier T, Schluter EW, Tabot GA, Miller LE, Tenore FV, Bensmaia SJ. Long-term stability of sensitivity to intracortical microstimulation of somatosensory cortex. J Neural Eng 2015; 12:056010. [DOI: 10.1088/1741-2560/12/5/056010] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Nolta NF, Christensen MB, Crane PD, Skousen JL, Tresco PA. BBB leakage, astrogliosis, and tissue loss correlate with silicon microelectrode array recording performance. Biomaterials 2015; 53:753-62. [DOI: 10.1016/j.biomaterials.2015.02.081] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 02/13/2015] [Accepted: 02/19/2015] [Indexed: 10/23/2022]
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65
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Kim S, Callier T, Tabot GA, Tenore FV, Bensmaia SJ. Sensitivity to microstimulation of somatosensory cortex distributed over multiple electrodes. Front Syst Neurosci 2015; 9:47. [PMID: 25914630 PMCID: PMC4392613 DOI: 10.3389/fnsys.2015.00047] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 03/07/2015] [Indexed: 01/09/2023] Open
Abstract
Meaningful and repeatable tactile sensations can be evoked by electrically stimulating primary somatosensory cortex. Intracortical microstimulation (ICMS) may thus be a viable approach to restore the sense of touch in individuals who have lost it, for example tetraplegic patients. One of the potential limitations of this approach, however, is that high levels of current can damage the neuronal tissue if the resulting current densities are too high. The limited range of safe ICMS amplitudes thus limits the dynamic range of ICMS-evoked sensations. One way to get around this limitation would be to distribute the ICMS over multiple electrodes in the hopes of intensifying the resulting percept without increasing the current density experienced by the neuronal tissue. Here, we test whether stimulating through multiple electrodes is a viable solution to increase the dynamic range of ICMS-elicited sensations without increasing the peak current density. To this end, we compare the ability of non-human primates to detect ICMS delivered through one vs. multiple electrodes. We also compare their ability to discriminate pulse trains differing in amplitude when these are delivered through one or more electrodes. We find that increasing the number of electrodes through which ICMS is delivered only has a marginal effect on detectability or discriminability despite the fact that 2-4 times more current is delivered overall. Furthermore, the impact of multielectrode stimulation (or lack thereof) is found whether pulses are delivered synchronously or asynchronously, whether the leading phase of the pulses is cathodic or anodic, and regardless of the spatial configuration of the electrode groups.
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Affiliation(s)
- Sungshin Kim
- Department of Organismal Biology and Anatomy, University of Chicago Chicago, IL, USA
| | - Thierri Callier
- Department of Organismal Biology and Anatomy, University of Chicago Chicago, IL, USA
| | - Gregg A Tabot
- Committee on Computational Neuroscience, University of Chicago Chicago, IL, USA
| | - Francesco V Tenore
- Research and Exploratory Development Department, Johns Hopkins University Applied Physics Laboratory Laurel, MD, USA
| | - Sliman J Bensmaia
- Department of Organismal Biology and Anatomy, University of Chicago Chicago, IL, USA ; Committee on Computational Neuroscience, University of Chicago Chicago, IL, USA
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Kolarcik CL, Catt K, Rost E, Albrecht IN, Bourbeau D, Du Z, Kozai TDY, Luo X, Weber DJ, Cui XT. Evaluation of poly(3,4-ethylenedioxythiophene)/carbon nanotube neural electrode coatings for stimulation in the dorsal root ganglion. J Neural Eng 2014; 12:016008. [PMID: 25485675 DOI: 10.1088/1741-2560/12/1/016008] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
OBJECTIVE The dorsal root ganglion is an attractive target for implanting neural electrode arrays that restore sensory function or provide therapy via stimulation. However, penetrating microelectrodes designed for these applications are small and deliver low currents. For long-term performance of microstimulation devices, novel coating materials are needed in part to decrease impedance values at the electrode-tissue interface and to increase charge storage capacity. APPROACH Conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-wall carbon nanotubes (CNTs) were coated on the electrode surface and doped with the anti-inflammatory drug, dexamethasone. Electrode characteristics and the tissue reaction around neural electrodes as a result of stimulation, coating and drug release were characterized. Hematoxylin and eosin staining along with antibodies recognizing Iba1 (microglia/macrophages), NF200 (neuronal axons), NeuN (neurons), vimentin (fibroblasts), caspase-3 (cell death) and L1 (neural cell adhesion molecule) were used. Quantitative image analyses were performed using MATLAB. MAIN RESULTS Our results indicate that coated microelectrodes have lower in vitro and in vivo impedance values. Significantly less neuronal death/damage was observed with coated electrodes as compared to non-coated controls. The inflammatory response with the PEDOT/CNT-coated electrodes was also reduced. SIGNIFICANCE This study is the first to report on the utility of these coatings in stimulation applications. Our results indicate PEDOT/CNT coatings may be valuable additions to implantable electrodes used as therapeutic modalities.
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Affiliation(s)
- Christi L Kolarcik
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA. Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, PA, USA. McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
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Lewis PM, Ackland HM, Lowery AJ, Rosenfeld JV. Restoration of vision in blind individuals using bionic devices: a review with a focus on cortical visual prostheses. Brain Res 2014; 1595:51-73. [PMID: 25446438 DOI: 10.1016/j.brainres.2014.11.020] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 11/05/2014] [Accepted: 11/08/2014] [Indexed: 12/13/2022]
Abstract
The field of neurobionics offers hope to patients with sensory and motor impairment. Blindness is a common cause of major sensory loss, with an estimated 39 million people worldwide suffering from total blindness in 2010. Potential treatment options include bionic devices employing electrical stimulation of the visual pathways. Retinal stimulation can restore limited visual perception to patients with retinitis pigmentosa, however loss of retinal ganglion cells precludes this approach. The optic nerve, lateral geniculate nucleus and visual cortex provide alternative stimulation targets, with several research groups actively pursuing a cortically-based device capable of driving several hundred stimulating electrodes. While great progress has been made since the earliest works of Brindley and Dobelle in the 1960s and 1970s, significant clinical, surgical, psychophysical, neurophysiological, and engineering challenges remain to be overcome before a commercially-available cortical implant will be realized. Selection of candidate implant recipients will require assessment of their general, psychological and mental health, and likely responses to visual cortex stimulation. Implant functionality, longevity and safety may be enhanced by careful electrode insertion, optimization of electrical stimulation parameters and modification of immune responses to minimize or prevent the host response to the implanted electrodes. Psychophysical assessment will include mapping the positions of potentially several hundred phosphenes, which may require repetition if electrode performance deteriorates over time. Therefore, techniques for rapid psychophysical assessment are required, as are methods for objectively assessing the quality of life improvements obtained from the implant. These measures must take into account individual differences in image processing, phosphene distribution and rehabilitation programs that may be required to optimize implant functionality. In this review, we detail these and other challenges facing developers of cortical visual prostheses in addition to briefly outlining the epidemiology of blindness, and the history of cortical electrical stimulation in the context of visual prosthetics.
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Affiliation(s)
- Philip M Lewis
- Department of Neurosurgery, Alfred Hospital, Melbourne, Australia; Department of Surgery, Monash University, Central Clinical School, Melbourne, Australia; Monash Vision Group, Faculty of Engineering, Monash University, Melbourne, Australia; Monash Institute of Medical Engineering, Monash University, Melbourne, Australia.
| | - Helen M Ackland
- Department of Neurosurgery, Alfred Hospital, Melbourne, Australia; Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
| | - Arthur J Lowery
- Monash Vision Group, Faculty of Engineering, Monash University, Melbourne, Australia; Monash Institute of Medical Engineering, Monash University, Melbourne, Australia; Department of Electrical and Computer Systems Engineering, Faculty of Engineering, Monash University, Melbourne, Australia.
| | - Jeffrey V Rosenfeld
- Department of Neurosurgery, Alfred Hospital, Melbourne, Australia; Department of Surgery, Monash University, Central Clinical School, Melbourne, Australia; Monash Vision Group, Faculty of Engineering, Monash University, Melbourne, Australia; Monash Institute of Medical Engineering, Monash University, Melbourne, Australia; F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, USA.
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Klaes C, Shi Y, Kellis S, Minxha J, Revechkis B, Andersen RA. A cognitive neuroprosthetic that uses cortical stimulation for somatosensory feedback. J Neural Eng 2014; 11:056024. [PMID: 25242377 DOI: 10.1088/1741-2560/11/5/056024] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Present day cortical brain-machine interfaces (BMIs) have made impressive advances using decoded brain signals to control extracorporeal devices. Although BMIs are used in a closed-loop fashion, sensory feedback typically is visual only. However medical case studies have shown that the loss of somesthesis in a limb greatly reduces the agility of the limb even when visual feedback is available. APPROACH To overcome this limitation, this study tested a closed-loop BMI that utilizes intracortical microstimulation to provide 'tactile' sensation to a non-human primate. MAIN RESULT Using stimulation electrodes in Brodmann area 1 of somatosensory cortex (BA1) and recording electrodes in the anterior intraparietal area, the parietal reach region and dorsal area 5 (area 5d), it was found that this form of feedback can be used in BMI tasks. SIGNIFICANCE Providing somatosensory feedback has the poyential to greatly improve the performance of cognitive neuroprostheses especially for fine control and object manipulation. Adding stimulation to a BMI system could therefore improve the quality of life for severely paralyzed patients.
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Andersen RA, Kellis S, Klaes C, Aflalo T. Toward more versatile and intuitive cortical brain-machine interfaces. Curr Biol 2014; 24:R885-R897. [PMID: 25247368 PMCID: PMC4410026 DOI: 10.1016/j.cub.2014.07.068] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Brain-machine interfaces have great potential for the development of neuroprosthetic applications to assist patients suffering from brain injury or neurodegenerative disease. One type of brain-machine interface is a cortical motor prosthetic, which is used to assist paralyzed subjects. Motor prosthetics to date have typically used the motor cortex as a source of neural signals for controlling external devices. The review will focus on several new topics in the arena of cortical prosthetics. These include using: recordings from cortical areas outside motor cortex; local field potentials as a source of recorded signals; somatosensory feedback for more dexterous control of robotics; and new decoding methods that work in concert to form an ecology of decode algorithms. These new advances promise to greatly accelerate the applicability and ease of operation of motor prosthetics.
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Affiliation(s)
- Richard A Andersen
- Division of Biology and Biological Engineering, California Institute of Technology, Mail Code 216-76, Pasadena, CA, 91125-7600, USA.
| | - Spencer Kellis
- Division of Biology and Biological Engineering, California Institute of Technology, Mail Code 216-76, Pasadena, CA, 91125-7600, USA
| | - Christian Klaes
- Division of Biology and Biological Engineering, California Institute of Technology, Mail Code 216-76, Pasadena, CA, 91125-7600, USA
| | - Tyson Aflalo
- Division of Biology and Biological Engineering, California Institute of Technology, Mail Code 216-76, Pasadena, CA, 91125-7600, USA
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Restoring tactile and proprioceptive sensation through a brain interface. Neurobiol Dis 2014; 83:191-8. [PMID: 25201560 DOI: 10.1016/j.nbd.2014.08.029] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 08/08/2014] [Accepted: 08/27/2014] [Indexed: 11/21/2022] Open
Abstract
Somatosensation plays a critical role in the dexterous manipulation of objects, in emotional communication, and in the embodiment of our limbs. For upper-limb neuroprostheses to be adopted by prospective users, prosthetic limbs will thus need to provide sensory information about the position of the limb in space and about objects grasped in the hand. One approach to restoring touch and proprioception consists of electrically stimulating neurons in somatosensory cortex in the hopes of eliciting meaningful sensations to support the dexterous use of the hands, promote their embodiment, and perhaps even restore the affective dimension of touch. In this review, we discuss the importance of touch and proprioception in everyday life, then describe approaches to providing artificial somatosensory feedback through intracortical microstimulation (ICMS). We explore the importance of biomimicry--the elicitation of naturalistic patterns of neuronal activation--and that of adaptation--the brain's ability to adapt to novel sensory input, and argue that both biomimicry and adaptation will play a critical role in the artificial restoration of somatosensation. We also propose that the documented re-organization that occurs after injury does not pose a significant obstacle to brain interfaces. While still at an early stage of development, sensory restoration is a critical step in transitioning upper-limb neuroprostheses from the laboratory to the clinic.
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Bensmaia SJ, Miller LE. Restoring sensorimotor function through intracortical interfaces: progress and looming challenges. Nat Rev Neurosci 2014; 15:313-25. [PMID: 24739786 DOI: 10.1038/nrn3724] [Citation(s) in RCA: 219] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The loss of a limb or paralysis resulting from spinal cord injury has devastating consequences on quality of life. One approach to restoring lost sensory and motor abilities in amputees and patients with tetraplegia is to supply them with implants that provide a direct interface with the CNS. Such brain-machine interfaces might enable a patient to exert voluntary control over a prosthetic or robotic limb or over the electrically induced contractions of paralysed muscles. A parallel interface could convey sensory information about the consequences of these movements back to the patient. Recent developments in the algorithms that decode motor intention from neuronal activity and in approaches to convey sensory feedback by electrically stimulating neurons, using biomimetic and adaptation-based approaches, have shown the promise of invasive interfaces with sensorimotor cortices, although substantial challenges remain.
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Affiliation(s)
- Sliman J Bensmaia
- Department of Organismal Biology and Anatomy, and Committee on Computational Neuroscience, University of Chicago, Chicago, Illinois 60637, USA
| | - Lee E Miller
- 1] Department of Physical Medicine and Rehabilitation, and Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA. [2] Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, USA
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Fisher LE, Ayers CA, Ciollaro M, Ventura V, Weber DJ, Gaunt RA. Chronic recruitment of primary afferent neurons by microstimulation in the feline dorsal root ganglia. J Neural Eng 2014; 11:036007. [DOI: 10.1088/1741-2560/11/3/036007] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Chen KH, Dammann JF, Boback JL, Tenore FV, Otto KJ, Gaunt RA, Bensmaia SJ. The effect of chronic intracortical microstimulation on the electrode-tissue interface. J Neural Eng 2014; 11:026004. [PMID: 24503702 PMCID: PMC8129589 DOI: 10.1088/1741-2560/11/2/026004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Somatosensation is critical for effective object manipulation, but current upper limb prostheses do not provide such feedback to the user. For individuals who require use of prosthetic limbs, this lack of feedback transforms a mundane task into one that requires extreme concentration and effort. Although vibrotactile motors and sensory substitution devices can be used to convey gross sensations, a direct neural interface is required to provide detailed and intuitive sensory feedback. The viability of intracortical microstimulation (ICMS) as a method to deliver feedback depends in part on the long-term reliability of implanted electrodes used to deliver the stimulation. The objective of the present study is to investigate the effects of chronic ICMS on the electrode-tissue interface. APPROACH We stimulate the primary somatosensory cortex of three Rhesus macaques through chronically implanted electrodes for 4 h per day over a period of six months, with different electrodes subjected to different regimes of stimulation. We measure the impedance and voltage excursion as a function of time and of ICMS parameters. We also test the sensorimotor consequences of chronic ICMS by having animals grasp and manipulate small treats. MAIN RESULTS We show that impedance and voltage excursion both decay with time but stabilize after 10-12 weeks. The magnitude of this decay is dependent on the amplitude of the ICMS and, to a lesser degree, the duration of individual pulse trains. Furthermore, chronic ICMS does not produce any deficits in fine motor control. SIGNIFICANCE The results suggest that chronic ICMS has only a minor effect on the electrode-tissue interface and may thus be a viable means to convey sensory feedback in neuroprosthetics.
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Affiliation(s)
- Kevin H Chen
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA
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Kaiser O, Aliuos P, Wissel K, Lenarz T, Werner D, Reuter G, Kral A, Warnecke A. Dissociated neurons and glial cells derived from rat inferior colliculi after digestion with papain. PLoS One 2013; 8:e80490. [PMID: 24349001 PMCID: PMC3861243 DOI: 10.1371/journal.pone.0080490] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 10/13/2013] [Indexed: 01/10/2023] Open
Abstract
The formation of gliosis around implant electrodes for deep brain stimulation impairs electrode–tissue interaction. Unspecific growth of glial tissue around the electrodes can be hindered by altering physicochemical material properties. However, in vitro screening of neural tissue–material interaction requires an adequate cell culture system. No adequate model for cells dissociated from the inferior colliculus (IC) has been described and was thus the aim of this study. Therefore, IC were isolated from neonatal rats (P3_5) and a dissociated cell culture was established. In screening experiments using four dissociation methods (Neural Tissue Dissociation Kit [NTDK] T, NTDK P; NTDK PN, and a validated protocol for the dissociation of spiral ganglion neurons [SGN]), the optimal media, and seeding densities were identified. Thereafter, a dissociation protocol containing only the proteolytic enzymes of interest (trypsin or papain) was tested. For analysis, cells were fixed and immunolabeled using glial- and neuron-specific antibodies. Adhesion and survival of dissociated neurons and glial cells isolated from the IC were demonstrated in all experimental settings. Hence, preservation of type-specific cytoarchitecture with sufficient neuronal networks only occurred in cultures dissociated with NTDK P, NTDK PN, and fresh prepared papain solution. However, cultures obtained after dissociation with papain, seeded at a density of 2×104 cells/well and cultivated with Neuro Medium for 6 days reliably revealed the highest neuronal yield with excellent cytoarchitecture of neurons and glial cells. The herein described dissociated culture can be utilized as in vitro model to screen interactions between cells of the IC and surface modifications of the electrode.
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Affiliation(s)
- Odett Kaiser
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Pooyan Aliuos
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Kirsten Wissel
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Thomas Lenarz
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Darja Werner
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Günter Reuter
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Andrej Kral
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Athanasia Warnecke
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
- * E-mail:
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Bari BA, Ollerenshaw DR, Millard DC, Wang Q, Stanley GB. Behavioral and electrophysiological effects of cortical microstimulation parameters. PLoS One 2013; 8:e82170. [PMID: 24340002 PMCID: PMC3855396 DOI: 10.1371/journal.pone.0082170] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 10/30/2013] [Indexed: 11/23/2022] Open
Abstract
Electrical microstimulation has been widely used to artificially activate neural circuits on fast time scales. Despite the ubiquity of its use, little is known about precisely how it activates neural pathways. Current is typically delivered to neural tissue in a manner that provides a locally balanced injection of positive and negative charge, resulting in negligible net charge delivery to avoid the neurotoxic effects of charge accumulation. Modeling studies have suggested that the most common approach, using a temporally symmetric current pulse waveform as the base unit of stimulation, results in preferential activation of axons, causing diffuse activation of neurons relative to the stimulation site. Altering waveform shape and using an asymmetric current pulse waveform theoretically reverses this bias and preferentially activates cell bodies, providing increased specificity. In separate studies, measurements of downstream cortical activation from sub-cortical microstimulation are consistent with this hypothesis, as are recent measurements of behavioral detection threshold currents from cortical microstimulation. Here, we compared the behavioral and electrophysiological effects of symmetric vs. asymmetric current waveform shape in cortical microstimulation. Using a go/no-go behavioral task, we found that microstimulation waveform shape significantly shifts psychometric performance, where a larger current pulse was necessary when applying an asymmetric waveform to elicit the same behavioral response, across a large range of behaviorally relevant current amplitudes. Using voltage-sensitive dye imaging of cortex in anesthetized animals with simultaneous cortical microstimulation, we found that altering microstimulation waveform shape shifted the cortical activation in a manner that mirrored the behavioral results. Taken together, these results are consistent with the hypothesis that asymmetric stimulation preferentially activates cell bodies, albeit at a higher threshold, as compared to symmetric stimulation. These findings demonstrate the sensitivity of the pathway to varying electrical stimulation parameters and underscore the importance of designing electrical stimuli for optimal activation of neural circuits.
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Affiliation(s)
- Bilal A. Bari
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
| | - Douglas R. Ollerenshaw
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
| | - Daniel C. Millard
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
| | - Qi Wang
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
| | - Garrett B. Stanley
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States of America
- * E-mail:
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76
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Calixto R, Salamat B, Rode T, Hartmann T, Volckaerts B, Ruther P, Lenarz T, Lim HH. Investigation of a new electrode array technology for a central auditory prosthesis. PLoS One 2013; 8:e82148. [PMID: 24312638 PMCID: PMC3846787 DOI: 10.1371/journal.pone.0082148] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 10/30/2013] [Indexed: 11/21/2022] Open
Abstract
Ongoing clinical studies on patients recently implanted with the auditory midbrain implant (AMI) into the inferior colliculus (IC) for hearing restoration have shown that these patients do not achieve performance levels comparable to cochlear implant patients. The AMI consists of a single-shank array (20 electrodes) for stimulation along the tonotopic axis of the IC. Recent findings suggest that one major limitation in AMI performance is the inability to sufficiently activate neurons across the three-dimensional (3-D) IC. Unfortunately, there are no currently available 3-D array technologies that can be used for clinical applications. More recently, there has been a new initiative by the European Commission to fund and develop 3-D chronic electrode arrays for science and clinical applications through the NeuroProbes project that can overcome the bulkiness and limited 3-D configurations of currently available array technologies. As part of the NeuroProbes initiative, we investigated whether their new array technology could be potentially used for future AMI patients. Since the NeuroProbes technology had not yet been tested for electrical stimulation in an in vivo animal preparation, we performed experiments in ketamine-anesthetized guinea pigs in which we inserted and stimulated a NeuroProbes array within the IC and recorded the corresponding neural activation within the auditory cortex. We used 2-D arrays for this initial feasibility study since they were already available and were sufficient to access the IC and also demonstrate effective activation of the central auditory system. Based on these encouraging results and the ability to develop customized 3-D arrays with the NeuroProbes technology, we can further investigate different stimulation patterns across the ICC to improve AMI performance.
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Affiliation(s)
- Roger Calixto
- Institute of Audioneurotechnology and Department of Experimental Otology, Hannover Medical University, Hannover, Germany
- * E-mail:
| | - Behrouz Salamat
- Institute of Audioneurotechnology and Department of Experimental Otology, Hannover Medical University, Hannover, Germany
| | - Thilo Rode
- Institute of Audioneurotechnology and Department of Experimental Otology, Hannover Medical University, Hannover, Germany
| | - Tanja Hartmann
- Institute of Audioneurotechnology and Department of Experimental Otology, Hannover Medical University, Hannover, Germany
| | | | - Patrick Ruther
- Department of Microsystems Engineering (IMTEK) at the University of Freiburg, Freiburg, Germany
| | - Thomas Lenarz
- Institute of Audioneurotechnology and Department of Experimental Otology, Hannover Medical University, Hannover, Germany
| | - Hubert H. Lim
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota
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Akhavan O, Ghaderi E. Flash photo stimulation of human neural stem cells on graphene/TiO2 heterojunction for differentiation into neurons. NANOSCALE 2013; 5:10316-26. [PMID: 24056702 DOI: 10.1039/c3nr02161k] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
For the application of human neural stem cells (hNSCs) in neural regeneration and brain repair, it is necessary to stimulate hNSC differentiation towards neurons rather than glia. Due to the unique properties of graphene in stem cell differentiation, here we introduce reduced graphene oxide (rGO)/TiO2 heterojunction film as a biocompatible flash photo stimulator for effective differentiation of hNSCs into neurons. Using the stimulation, the number of cell nuclei on rGO/TiO2 increased by a factor of ~1.5, while on GO/TiO2 and TiO2 it increased only ~48 and 24%, respectively. Moreover, under optimum conditions of flash photo stimulation (10 mW cm(-2) flash intensity and 15.0 mM ascorbic acid in cell culture medium) not only did the number of cell nuclei and neurons differentiated on rGO/TiO2 significantly increase (by factors of ~2.5 and 3.6), but also the number of glial cells decreased (by a factor of ~0.28). This resulted in a ~23-fold increase in the neural to glial cell ratio. Such highly accelerated differentiation was assigned to electron injection from the photoexcited TiO2 into the cells on the rGO through Ti-C and Ti-O-C bonds. The role of ascorbic acid, as a scavenger of the photoexcited holes, in flash photo stimulation was studied at various concentrations and flash intensities.
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Affiliation(s)
- Omid Akhavan
- Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran.
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Zaaimi B, Ruiz-Torres R, Solla SA, Miller LE. Multi-electrode stimulation in somatosensory cortex increases probability of detection. J Neural Eng 2013; 10:056013. [PMID: 23985904 DOI: 10.1088/1741-2560/10/5/056013] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Brain machine interfaces (BMIs) that decode control signals from motor cortex have developed tremendously in the past decade, but virtually all rely exclusively on vision to provide feedback. There is now increasing interest in developing an afferent interface to replace natural somatosensation, much as the cochlear implant has done for the sense of hearing. Preliminary experiments toward a somatosensory neuroprosthesis have mostly addressed the sense of touch, but proprioception, the sense of limb position and movement, is also critical for the control of movement. However, proprioceptive areas of cortex lack the precise somatotopy of tactile areas. We showed previously that there is only a weak tendency for neighboring neurons in area 2 to signal similar directions of hand movement. Consequently, stimulation with the relatively large currents used in many studies is likely to activate a rather heterogeneous set of neurons. APPROACH Here, we have compared the effect of single-electrode stimulation at subthreshold levels to the effect of stimulating as many as seven electrodes in combination. MAIN RESULTS We found a mean enhancement in the sensitivity to the stimulus (d') of 0.17 for pairs compared to individual electrodes (an increase of roughly 30%), and an increase of 2.5 for groups of seven electrodes (260%). SIGNIFICANCE We propose that a proprioceptive interface made up of several hundred electrodes may yield safer, more effective sensation than a BMI using fewer electrodes and larger currents.
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Affiliation(s)
- Boubker Zaaimi
- Department of Physiology, Northwestern University, Chicago, IL 60611, USA
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Wang C, Brunton E, Haghgooie S, Cassells K, Lowery A, Rajan R. Characteristics of electrode impedance and stimulation efficacy of a chronic cortical implant using novel annulus electrodes in rat motor cortex. J Neural Eng 2013; 10:046010. [PMID: 23819958 DOI: 10.1088/1741-2560/10/4/046010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Cortical neural prostheses with implanted electrode arrays have been used to restore compromised brain functions but concerns remain regarding their long-term stability and functional performance. APPROACH Here we report changes in electrode impedance and stimulation thresholds for a custom-designed electrode array implanted in rat motor cortex for up to three months. MAIN RESULTS The array comprises four 2000 µm long electrodes with a large annular stimulating surface (7860-15700 µm(2)) displaced from the penetrating insulated tip. Compared to pre-implantation in vitro values there were three phases of impedance change: (1) an immediate large increase of impedance by an average of two-fold on implantation; (2) a period of continued impedance increase, albeit with considerable variability, which reached a peak at approximately four weeks post-implantation and remained high over the next two weeks; (3) finally, a period of 5-6 weeks when impedance stabilized at levels close to those seen immediately post-implantation. Impedance could often be temporarily decreased by applying brief trains of current stimulation, used to evoke motor output. The stimulation threshold to induce observable motor behaviour was generally between 75-100 µA, with charge density varying from 48-128 µC cm(-2), consistent with the lower current density generated by electrodes with larger stimulating surface area. No systematic change in thresholds occurred over time, suggesting that device functionality was not compromised by the factors that caused changes in electrode impedance. SIGNIFICANCE The present results provide support for the use of annulus electrodes in future applications in cortical neural prostheses.
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Affiliation(s)
- Chun Wang
- Monash Vision Group and Department of Physiology, Monash University, Clayton, VIC 3168, Australia.
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Collinger JL, Foldes S, Bruns TM, Wodlinger B, Gaunt R, Weber DJ. Neuroprosthetic technology for individuals with spinal cord injury. J Spinal Cord Med 2013; 36:258-72. [PMID: 23820142 PMCID: PMC3758523 DOI: 10.1179/2045772313y.0000000128] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
CONTEXT Spinal cord injury (SCI) results in a loss of function and sensation below the level of the lesion. Neuroprosthetic technology has been developed to help restore motor and autonomic functions as well as to provide sensory feedback. FINDINGS This paper provides an overview of neuroprosthetic technology that aims to address the priorities for functional restoration as defined by individuals with SCI. We describe neuroprostheses that are in various stages of preclinical development, clinical testing, and commercialization including functional electrical stimulators, epidural and intraspinal microstimulation, bladder neuroprosthesis, and cortical stimulation for restoring sensation. We also discuss neural recording technologies that may provide command or feedback signals for neuroprosthetic devices. CONCLUSION/CLINICAL RELEVANCE Neuroprostheses have begun to address the priorities of individuals with SCI, although there remains room for improvement. In addition to continued technological improvements, closing the loop between the technology and the user may help provide intuitive device control with high levels of performance.
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81
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Kane SR, Cogan SF, Ehrlich J, Plante TD, McCreery DB, Troyk PR. Electrical performance of penetrating microelectrodes chronically implanted in cat cortex. IEEE Trans Biomed Eng 2013; 60:2153-60. [PMID: 23475329 DOI: 10.1109/tbme.2013.2248152] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Penetrating microelectrode arrays with 2000 μm (2) sputtered iridium oxide (SIROF) electrode sites were implanted in cat cerebral cortex, and their long-term electrochemical performance evaluated in vivo by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and current pulsing. Measurements were made from days 33 to 328 postimplantation. The CV-defined charge storage capacity, measured at 50 mV/s, increased linearly with time over the course of implantation for two arrays and was unchanged for one array. A modest decrease in 1 kHz impedance was also observed. These results suggest an ongoing increase in the apparent electrochemical surface area of the electrodes, which is attributed to electrical leakage pathways arising from cracking of Parylene insulation observed by SEM of explanted arrays. During current pulsing with a 0.0 V interpulse bias, the electrodes readily delivered 8 nC/phase in vitro, but some channels approached or exceeded the water reduction potential during in vivo pulsing. The charge injection capacity in vivo increased linearly with the interpulse bias (0-0.6 V Ag\vert AgCl) from 11.5 to 21.8 nC/ph and with pulse width (150-500 μs) from 8.8 to 14 nC/ph (at 0.0 V bias). These values are lower than those determined from measurements in buffered physiological saline, emphasizing the importance of in vivo measurements in assessing chronic electrode performance. The consequence of current leakage pathways on the charge-injection measurements is also discussed.
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Abstract
Artificial sensation via electrical or optical stimulation of brain sensory areas offers a promising treatment for sensory deficits. For a brain-machine-brain interface, such artificial sensation conveys feedback signals from a sensorized prosthetic limb. The ways neural tissue can be stimulated to evoke artificial sensation and the parameter space of such stimulation, however, remain largely unexplored. Here we investigated whether stochastic facilitation (SF) could enhance an artificial tactile sensation produced by intracortical microstimulation (ICMS). Two rhesus monkeys learned to use a virtual hand, which they moved with a joystick, to explore virtual objects on a computer screen. They sought an object associated with a particular artificial texture (AT) signaled by a periodic ICMS pattern delivered to the primary somatosensory cortex (S1) through a pair of implanted electrodes. During each behavioral trial, aperiodic ICMS (i.e., noise) of randomly chosen amplitude was delivered to S1 through another electrode pair implanted 1 mm away from the site of AT delivery. Whereas high-amplitude noise worsened AT detection, moderate noise clearly improved the detection of weak signals, significantly raising the proportion of correct trials. These findings suggest that SF could be used to enhance prosthetic sensation.
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83
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Daly J, Liu J, Aghagolzadeh M, Oweiss K. Optimal space-time precoding of artificial sensory feedback through mutichannel microstimulation in bi-directional brain-machine interfaces. J Neural Eng 2012; 9:065004. [PMID: 23187009 PMCID: PMC5988221 DOI: 10.1088/1741-2560/9/6/065004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Brain-machine interfaces (BMIs) aim to restore lost sensorimotor and cognitive function in subjects with severe neurological deficits. In particular, lost somatosensory function may be restored by artificially evoking patterns of neural activity through microstimulation to induce perception of tactile and proprioceptive feedback to the brain about the state of the limb. Despite an early proof of concept that subjects could learn to discriminate a limited vocabulary of intracortical microstimulation (ICMS) patterns that instruct the subject about the state of the limb, the dynamics of a moving limb are unlikely to be perceived by an arbitrarily-selected, discrete set of static microstimulation patterns, raising questions about the generalization and the scalability of this approach. In this work, we propose a microstimulation protocol intended to activate optimally the ascending somatosensory pathway. The optimization is achieved through a space-time precoder that maximizes the mutual information between the sensory feedback indicating the limb state and the cortical neural response evoked by thalamic microstimulation. Using a simplified multi-input multi-output model of the thalamocortical pathway, we show that this optimal precoder can deliver information more efficiently in the presence of noise compared to suboptimal precoders that do not account for the afferent pathway structure and/or cortical states. These results are expected to enhance the way microstimulation is used to induce somatosensory perception during sensorimotor control of artificial devices or paralyzed limbs.
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Affiliation(s)
- John Daly
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48823, U.S.A
| | - Jianbo Liu
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48823, U.S.A
| | - Mehdi Aghagolzadeh
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48823, U.S.A
| | - Karim Oweiss
- Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48823, U.S.A
- Neuroscience Program, Michigan State University, East Lansing, MI 48823, U.S.A
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Davis TS, Parker RA, House PA, Bagley E, Wendelken S, Normann RA, Greger B. Spatial and temporal characteristics of V1 microstimulation during chronic implantation of a microelectrode array in a behaving macaque. J Neural Eng 2012; 9:065003. [PMID: 23186948 PMCID: PMC3521049 DOI: 10.1088/1741-2560/9/6/065003] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE It has been hypothesized that a vision prosthesis capable of evoking useful visual percepts can be based upon electrically stimulating the primary visual cortex (V1) of a blind human subject via penetrating microelectrode arrays. As a continuation of earlier work, we examined several spatial and temporal characteristics of V1 microstimulation. APPROACH An array of 100 penetrating microelectrodes was chronically implanted in V1 of a behaving macaque monkey. Microstimulation thresholds were measured using a two-alternative forced choice detection task. Relative locations of electrically-evoked percepts were measured using a memory saccade-to-target task. MAIN RESULTS The principal finding was that two years after implantation we were able to evoke behavioural responses to electric stimulation across the spatial extent of the array using groups of contiguous electrodes. Consistent responses to stimulation were evoked at an average threshold current per electrode of 204 ± 49 µA (mean ± std) for groups of four electrodes and 91 ± 25 µA for groups of nine electrodes. Saccades to electrically-evoked percepts using groups of nine electrodes showed that the animal could discriminate spatially distinct percepts with groups having an average separation of 1.6 ± 0.3 mm (mean ± std) in cortex and 1.0° ± 0.2° in visual space. Significance. These results demonstrate chronic perceptual functionality and provide evidence for the feasibility of a cortically-based vision prosthesis for the blind using penetrating microelectrodes.
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Affiliation(s)
- T S Davis
- Department of Bioengineering, University of Utah, UT, USA
| | - R A Parker
- Interdepartmental Program in Neuroscience, University of Utah, UT, USA
| | - P A House
- Department of Neurosurgery, University of Utah, UT, USA
| | - E Bagley
- Department of Bioengineering, University of Utah, UT, USA
| | - S Wendelken
- Department of Bioengineering, University of Utah, UT, USA
| | - R A Normann
- Department of Bioengineering, University of Utah, UT, USA
- Department of Ophthalmology and Visual Sciences, University of Utah, UT, USA
| | - B Greger
- Department of Bioengineering, University of Utah, UT, USA
- Department of Ophthalmology and Visual Sciences, University of Utah, UT, USA
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85
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Neural stimulation for visual rehabilitation: advances and challenges. ACTA ACUST UNITED AC 2012; 107:421-31. [PMID: 23148976 DOI: 10.1016/j.jphysparis.2012.10.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 10/04/2012] [Accepted: 10/23/2012] [Indexed: 02/07/2023]
Abstract
Blindness affects tens of million people worldwide and its prevalence constantly increases along with population aging. In some pathologies leading to vision loss, prosthetic approaches are currently the only hope for the patient to recover some visual perception. Here, we review the latest advances in visual prosthetic strategies with their respective strength and weakness. The principle is to electrically stimulate neurons along the visual pathway. Ocular approaches target the remaining retinal cells whereas brain stimulation aims at stimulating higher visual structures directly. Even though ocular approaches are less invasive and easier to implement, brain stimulation can be applied to diseases where the connection between the retina and the brain is lost such as in glaucoma and could therefore benefit to patients with different pathologies. Today, numbers of groups are investigating these strategies and the first devices start being commercialized. However, critical bottlenecks still impair our scientific efforts towards efficient visual implants. These challenges include electrode miniaturization, material optimization, multiplexing of stimulation channels and encoding of visual information into electrical stimuli.
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86
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Brunton E, Lowery AJ, Rajan R. A comparison of microelectrodes for a visual cortical prosthesis using finite element analysis. FRONTIERS IN NEUROENGINEERING 2012; 5:23. [PMID: 23060789 PMCID: PMC3460534 DOI: 10.3389/fneng.2012.00023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 09/11/2012] [Indexed: 11/13/2022]
Abstract
Altering the geometry of microelectrodes for use in a cortical neural prosthesis modifies the electric field generated in tissue, thereby affecting electrode efficacy and tissue damage. Commonly, electrodes with an active region located at the tip (“conical” electrodes) are used for stimulation of cortex but there is argument to believe this geometry may not be the best. Here we use finite element analysis to compare the electric fields generated by three types of electrodes, a conical electrode with exposed active tip, an annular electrode with active area located up away from the tip, and a striped annular electrode where the active annular region has bands of insulation interrupting the full active region. The results indicate that the current density on the surface of the conical electrodes can be up to 10 times greater than the current density on the annular electrodes of the same height, which may increase the propensity for tissue damage. However choosing the most efficient electrode geometry in order to reduce power consumption is dependent on the distance of the electrode to the target neurons. If neurons are located within 10 μm of the electrode, then a small conical electrode would be more power efficient. On the other hand if the target neuron is greater than 500 μm away—as happens normally when insertion of an array of electrodes into cortex results in a “kill zone” around each electrode due to insertion damage and inflammatory responses—then a large annular electrode would be more efficient.
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Affiliation(s)
- Emma Brunton
- Department of Electrical and Computer Systems Engineering, Monash University Clayton, VIC, Australia ; Monash Vision Group, Monash University Clayton, VIC, Australia
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87
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Richardson AG, Fetz EE. Brain state-dependence of electrically evoked potentials monitored with head-mounted electronics. IEEE Trans Neural Syst Rehabil Eng 2012; 20:756-61. [PMID: 22801526 DOI: 10.1109/tnsre.2012.2204902] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Inferring changes in brain connectivity is critical to studies of learning-related plasticity and stimulus-induced conditioning of neural circuits. In addition, monitoring spontaneous fluctuations in connectivity can provide insight into information processing during different brain states. Here, we quantified state-dependent connectivity changes throughout the 24-h sleep-wake cycle in freely behaving monkeys. A novel, head-mounted electronic device was used to electrically stimulate at one site and record evoked potentials at other sites. Electrically evoked potentials (EEPs) revealed the connectivity pattern between several cortical sites and the basal forebrain. We quantified state-dependent changes in the EEPs. Cortico-cortical EEP amplitude increased during slow-wave sleep, compared to wakefulness, while basal-cortical EEP amplitude decreased. The results demonstrate the utility of using portable electronics to document state-dependent connectivity changes in freely behaving primates.
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Affiliation(s)
- Andrew G Richardson
- Department of Physiology and Biophysics and Washington National Primate Research Center, University of Washington, Seattle, WA 98195, USA
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88
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Koivuniemi AS, Regele OB, Brenner JH, Otto KJ. Rat behavioral model for high-throughput parametric studies of intracortical microstimulation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:7541-4. [PMID: 22256083 DOI: 10.1109/iembs.2011.6091859] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the development of sensory prosthetic devices based on intracortical microstimulation (ICMS) an important objective is to optimize the stimulus waveform. However, because of the large design space such optimization is an imposing challenge. This study highlights the ability of individual rats, trained using a conditioned avoidance paradigm and performing an adaptive task, to generate highly consistent and significant data. Three experiments on the effects of phase delay, stimulus pulse rate, and waveform asymmetry were completed and revealed detailed and significant results. These results, consisting of 244 individual thresholds, were generated by one rat in 19 days.
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Affiliation(s)
- Andrew S Koivuniemi
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
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89
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Artificial vision through neuronal stimulation. Neurosci Lett 2012; 519:122-8. [PMID: 22342306 DOI: 10.1016/j.neulet.2012.01.063] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2011] [Accepted: 01/25/2012] [Indexed: 11/23/2022]
Abstract
INTRODUCTION The term visual prosthesis refers to any device capable of eliciting visual percepts in an individual through electrical stimulation of any part of the visual system. BACKGROUND Blindness can be due to eye pathology or due to damage of the lateral geniculate or visual cortex. Eye pathology other than diseases that affect the cornea and lens are numerous and some of the leading causes are diabetic retinopathy, age-related macular degeneration, retinal detachment, glaucoma, and retinal vascular occlusions. The visual prosthesis can be divided into non-retinal and retinal approaches. Non-retinal approaches include cortical and optic nerve prosthesis. Retinal approaches are aimed at eye pathologies in which at least part of the optic nerve remains intact whereas when the optic nerve is nearly completely damaged and/or the eye itself is disfigured or degenerated then a non-retinal approach is warranted. The retinal prosthesis can be placed on the surface of the retina, in the subretinal space or in the suprachoroidal space. RESULTS Several independent groups related variable degrees of success in promoting visual sensations through electrical stimulation of the visual system. Every technique, equipment and anatomical target has its advantages and disadvantages, and the biological/electrical-mechanical interface is still the aspect of the research towards a chronic, long term, reliable biomimetic implant. CONCLUSIONS The visual prostheses have achieved significant developments in recent years. We see continued improvement in visual acuity with increasing number and density of electrodes. Even though the visual acuity is still poor relative to normal vision, these subjects can read letters using their implants. Perhaps more importantly, blind patients can use these devices for mobility and orientation.
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90
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Han M, Manoonkitiwongsa PS, Wang CX, McCreery DB. In vivo validation of custom-designed silicon-based microelectrode arrays for long-term neural recording and stimulation. IEEE Trans Biomed Eng 2012; 59:346-54. [PMID: 22020666 PMCID: PMC3265636 DOI: 10.1109/tbme.2011.2172440] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We developed and validated silicon-based neural probes for neural stimulating and recording in long-term implantation in the brain. The probes combine the deep reactive ion etching process and mechanical shaping of their tip region, yielding a mechanically sturdy shank with a sharpened tip to reduce insertion force into the brain and spinal cord, particularly, with multiple shanks in the same array. The arrays' insertion forces have been quantified in vitro. Five consecutive chronically-implanted devices were fully functional from 3 to 18 months. The microelectrode sites were electroplated with iridium oxide, and the charge injection capacity measurements were performed both in vitro and after implantation in the adult feline brain. The functionality of the chronic array was validated by stimulating in the cochlear nucleus and recording the evoked neuronal activity in the central nucleus of the inferior colliculus. The arrays' recording quality has also been quantified in vivo with neuronal spike activity recorded up to 566 days after implantation. Histopathology evaluation of neurons and astrocytes using immunohistochemical stains indicated minimal alterations of tissue architecture after chronic implantation.
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Affiliation(s)
- Martin Han
- Huntington Medical Research Institutes, Pasadena, CA 91105 USA ()
| | | | - Cindy X. Wang
- Department of Mechanical Engineering, University of California, Berkeley, CA 94710 USA ()
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91
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Parker RA, Davis TS, House PA, Normann RA, Greger B. The functional consequences of chronic, physiologically effective intracortical microstimulation. PROGRESS IN BRAIN RESEARCH 2011; 194:145-65. [PMID: 21867801 DOI: 10.1016/b978-0-444-53815-4.00010-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
Many studies have demonstrated the ability of chronically implanted multielectrode arrays (MEAs) to extract information from the motor cortex of both humans and nonhuman primates. Similarly, many studies have shown the ability of intracortical microstimulation to impart information to the brain via a single or a few electrodes acutely implanted in sensory cortex of nonhuman primates, but relatively few microstimulation studies characterizing chronically implanted MEAs have been performed. Additionally, device and tissue damage have been reported at the levels of microstimulation used in these studies. Whether the damage resulting from microstimulation impairs the ability of MEAs to chronically produce physiological effects, however, has not been directly tested. In this study, we examined the functional consequences of multiple months of periodic microstimulation via chronically implanted MEAs at levels capable of evoking physiological responses, that is, electromyogram (EMG) activity. The functionality of the MEA and neural tissue was determined by measuring impedances, the ability of microstimulation to evoke EMG responses, and the recording of action potentials. We found that impedances and the number of recorded action potentials followed the previously reported trend of decreasing over time in both animals that received microstimulation and those which did not receive microstimulation. Despite these trends, the ability to evoke EMG responses and record action potentials was retained throughout the study. The results of this study suggest that intracortical microstimulation via MEAs did not cause functional failure, suggesting that MEA-based microstimulation is ready to transition into subchronic (< 30 days) human trials to determine whether complex spatiotemporal sensory percepts can be evoked by patterned microstimulation.
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Affiliation(s)
- Rebecca A Parker
- Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, UT, USA
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92
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Koivuniemi AS, Otto KJ. Asymmetric versus symmetric pulses for cortical microstimulation. IEEE Trans Neural Syst Rehabil Eng 2011; 19:468-76. [PMID: 21968793 DOI: 10.1109/tnsre.2011.2166563] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Intracortical microstimulation (ICMS), which has shown promise in the visual, auditory and somatosensory systems as a platform for sensory prostheses, typically relies on charged balanced, symmetric, biphasic stimulation. However, neural stimulation models as well as experiments conducted in cochlear implant users have suggested that charge balanced asymmetric pulses could generate lower detection thresholds for stimulation in terms of charge per phase. For this study, rats were chronically implanted with microelectrode arrays unilaterally in their right auditory cortex and then trained to detect ICMS delivered through a single electrode site in order to determine their behavioral threshold. This model was used in two experiments. The first experiment addressed the effect of lead phase direction, asymmetry, and phase duration on detection threshold. The second experiment fixed the cathode phase duration at 123 μs and varied only the phase asymmetry and lead phase direction. Taken together, the results of these experiments suggest that, for ICMS, the primary determinant of threshold level is cathode phase duration, and that asymmetry provides no significant advantage when compared to symmetric, cathode leading pulses. However, symmetric anode leading pulses of less than or equal to 205 μs per phase consistently showed higher thresholds when compared to all other pulses of equal cathode phase duration.
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Affiliation(s)
- Andrew S Koivuniemi
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
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93
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Abdo A, Sahin M, Freedman DS, Cevik E, Spuhler PS, Unlu MS. Floating light-activated microelectrical stimulators tested in the rat spinal cord. J Neural Eng 2011; 8:056012. [PMID: 21914931 DOI: 10.1088/1741-2560/8/5/056012] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Microelectrodes of neural stimulation utilize fine wires for electrical connections to driving electronics. Breakage of these wires and the neural tissue response due to their tethering forces are major problems encountered with long-term implantation of microelectrodes. The lifetime of an implant for neural stimulation can be substantially improved if the wire interconnects are eliminated. Thus, we proposed a floating light-activated microelectrical stimulator (FLAMES) for wireless neural stimulation. In this paradigm, a laser beam at near infrared (NIR) wavelengths will be used as a means of energy transfer to the device. In this study, microstimulators of various sizes were fabricated, with two cascaded GaAs p-i-n photodiodes, and tested in the rat spinal cord. A train of NIR pulses (0.2 ms, 50 Hz) was sent through the tissue to wirelessly activate the devices and generate the stimulus current. The forces elicited by intraspinal stimulation were measured from the ipsilateral forelimb with a force transducer. The largest forces were around 1.08 N, a significant level of force for the rat forelimb motor function. These in vivo tests suggest that the FLAMES can be used for intraspinal microstimulation even for the deepest implant locations in the rat spinal cord. The power required to generate a threshold arm movement was investigated as the laser source was moved away from the microstimulator. The results indicate that the photon density does not decrease substantially for horizontal displacements of the source that are in the same order as the beam radius. This gives confidence that the stimulation threshold may not be very sensitive to small displacement of the spinal cord relative to the spine-mounted optical power source.
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Affiliation(s)
- Ammar Abdo
- Biomedical Engineering Department, New Jersey Institute of Technology, NJ, USA
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94
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Muthuswamy J, Anand S, Sridharan A. Adaptive movable neural interfaces for monitoring single neurons in the brain. Front Neurosci 2011; 5:94. [PMID: 21927593 PMCID: PMC3168918 DOI: 10.3389/fnins.2011.00094] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Accepted: 07/14/2011] [Indexed: 01/23/2023] Open
Abstract
Implantable microelectrodes that are currently used to monitor neuronal activity in the brain in vivo have serious limitations both in acute and chronic experiments. Movable microelectrodes that adapt their position in the brain to maximize the quality of neuronal recording have been suggested and tried as a potential solution to overcome the challenges with the current fixed implantable microelectrodes. While the results so far suggest that movable microelectrodes improve the quality and stability of neuronal recordings from the brain in vivo, the bulky nature of the technologies involved in making these movable microelectrodes limits the throughput (number of neurons that can be recorded from at any given time) of these implantable devices. Emerging technologies involving the use of microscale motors and electrodes promise to overcome this limitation. This review summarizes some of the most recent efforts in developing movable neural interfaces using microscale technologies that adapt their position in response to changes in the quality of the neuronal recordings. Key gaps in our understanding of the brain-electrode interface are highlighted. Emerging discoveries in these areas will lead to success in the development of a reliable and stable interface with single neurons that will impact basic neurophysiological studies and emerging cortical prosthetic technologies.
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Affiliation(s)
- Jit Muthuswamy
- School of Biological and Health Systems Engineering, Arizona State University Tempe, AZ, USA
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95
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Torab K, Davis TS, Warren DJ, House PA, Normann RA, Greger B. Multiple factors may influence the performance of a visual prosthesis based on intracortical microstimulation: nonhuman primate behavioural experimentation. J Neural Eng 2011; 8:035001. [PMID: 21593550 DOI: 10.1088/1741-2560/8/3/035001] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We hypothesize that a visual prosthesis capable of evoking high-resolution visual perceptions can be produced using high-electrode-count arrays of penetrating microelectrodes implanted into the primary visual cortex of a blind human subject. To explore this hypothesis, and as a prelude to human psychophysical experiments, we have conducted a set of experiments in primary visual cortex (V1) of non-human primates using chronically implanted Utah Electrode Arrays (UEAs). The electrical and recording properties of implanted electrodes, the high-resolution visuotopic organization of V1, and the stimulation levels required to evoke behavioural responses were measured. The impedances of stimulated electrodes were found to drop significantly immediately following stimulation sessions, but these post-stimulation impedances returned to pre-stimulation values by the next experimental session. Two months of periodic microstimulation at currents of up to 96 µA did not impair the mapping of receptive fields from local field potentials or multi-unit activity, or impact behavioural visual thresholds of light stimuli that excited regions of V1 that were implanted with UEAs. These results demonstrate that microstimulation at the levels used did not cause functional impairment of the electrode array or the neural tissue. However, microstimulation with current levels ranging from 18 to 76 µA (46 ± 19 µA, mean ± std) was able to elicit behavioural responses on eight out of 82 systematically stimulated electrodes. We suggest that the ability of microstimulation to evoke phosphenes and elicit a subsequent behavioural response may depend on several factors: the location of the electrode tips within the cortical layers of V1, distance of the electrode tips to neuronal somata, and the inability of nonhuman primates to recognize and respond to a generalized set of evoked percepts.
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Affiliation(s)
- K Torab
- Department of Bioengineering, University of Utah, UT, USA
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96
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Musa S, Rand DR, Bartic C, Eberle W, Nuttin B, Borghs G. Coulometric detection of irreversible electrochemical reactions occurring at Pt microelectrodes used for neural stimulation. Anal Chem 2011; 83:4012-22. [PMID: 21545093 DOI: 10.1021/ac103037u] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The electrochemistry of 50 μm diameter Pt electrodes used for neural stimulation was studied in vitro by reciprocal derivative chronopotentiometry. This differential method provides well-defined electrochemical signatures of the various polarization phenomena that occur at Pt microelectrodes and are generally obscured in voltage transients. In combination with a novel in situ coulometric approach, irreversible H(2) and O(2) evolution, Pt dissolution and reduction of dissolved O(2) were detected. Measurements were performed with biphasic, charge-balanced, cathodic-first and anodic-first current pulses at charge densities ranging from 0.07 to 1.41 mC/cm(2) (real surface area) in phosphate buffered saline (PBS) with and without bovine serum albumin (BSA). The extent to which O(2) reduction occurs under the different stimulation conditions was compared in O(2)-saturated and deoxygenated PBS. Adsorption of BSA inhibited Pt dissolution as well as Pt oxidation and oxide reduction by blocking reactive sites on the electrode surface. This inhibitory effect promoted the onset of irreversible H(2) and O(2) evolution, which occurred at lower charge densities than those in PBS. Reduction of dissolved O(2) on Pt electrodes accounted for 19-34% of the total injected charge in O(2)-saturated PBS, while a contribution of 0.4-12% was estimated for in vivo stimulation. These result may prove important for the interpretation of histological damage induced by neural stimulation and therefore help define safer operational limits.
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Abstract
One of the roadblocks in the field of neural prosthetics is the lack of microelectronic devices for neural stimulation that can last a lifetime in the central nervous system. Wireless multi-electrode arrays are being developed to improve the longevity of implants by eliminating the wire interconnects as well as the chronic tissue reactions due to the tethering forces generated by these wires. An area of research that has not been sufficiently investigated is a simple single-channel passive microstimulator that can collect the stimulus energy that is transmitted wirelessly through the tissue and immediately convert it into the stimulus pulse. For example, many neural prosthetic approaches to intraspinal microstimulation require only a few channels of stimulation. Wired spinal cord implants are not practical for human subjects because of the extensive flexions and rotations that the spinal cord experiences. Thus, intraspinal microstimulation may be a pioneering application that can benefit from submillimeter-size floating stimulators. Possible means of energizing such a floating microstimulator, such as optical, acoustic, and electromagnetic waves, are discussed.
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Affiliation(s)
- Mesut Sahin
- Biomedical Engineering Department, New Jersey Institute of Technology, Newark, NJ 07102, USA.
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Heo C, Yoo J, Lee S, Jo A, Jung S, Yoo H, Lee YH, Suh M. The control of neural cell-to-cell interactions through non-contact electrical field stimulation using graphene electrodes. Biomaterials 2011; 32:19-27. [DOI: 10.1016/j.biomaterials.2010.08.095] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Accepted: 08/29/2010] [Indexed: 01/09/2023]
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