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Oz R, Edelman-Klapper H, Nivinsky-Margalit S, Slovin H. Microstimulation in the primary visual cortex: activity patterns and their relation to visual responses and evoked saccades. Cereb Cortex 2022; 33:5192-5209. [PMID: 36300613 DOI: 10.1093/cercor/bhac409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 09/22/2022] [Accepted: 09/22/2022] [Indexed: 11/12/2022] Open
Abstract
Abstract
Intracortical microstimulation (ICMS) in the primary visual cortex (V1) can generate the visual perception of a small point of light, termed phosphene, and evoke saccades directed to the receptive field of the stimulated neurons. Although ICMS is widely used, a direct measurement of the spatio-temporal patterns of neural activity evoked by ICMS and their relation to the neural responses evoked by visual stimuli or how they relate to ICMS-evoked saccades are still missing. To investigate this, we combined ICMS with voltage-sensitive dye imaging in V1 of behaving monkeys and measured neural activity at a high spatial (meso-scale) and temporal resolution. We then compared the population response evoked by small visual stimuli to those evoked by microstimulation. Both stimulation types evoked population activity that spread over few millimeters in V1 and propagated to extrastriate areas. However, the population responses evoked by ICMS have shown faster dynamics for the activation transients and the horizontal propagation of activity revealed a wave-like propagation. Finally, neural activity in the ICMS condition was higher for trials with evoked saccades as compared with trials without saccades. Our results uncover the spatio-temporal patterns evoked by ICMS and their relation to visual processing and saccade generation.
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Affiliation(s)
- Roy Oz
- The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University , Ramat Gan 5290002, Israel
| | - Hadar Edelman-Klapper
- The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University , Ramat Gan 5290002, Israel
| | - Shany Nivinsky-Margalit
- The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University , Ramat Gan 5290002, Israel
| | - Hamutal Slovin
- The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University , Ramat Gan 5290002, Israel
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2
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Motor-related signals support localization invariance for stable visual perception. PLoS Comput Biol 2022; 18:e1009928. [PMID: 35286305 PMCID: PMC8947590 DOI: 10.1371/journal.pcbi.1009928] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 03/24/2022] [Accepted: 02/16/2022] [Indexed: 11/19/2022] Open
Abstract
Our ability to perceive a stable visual world in the presence of continuous movements of the body, head, and eyes has puzzled researchers in the neuroscience field for a long time. We reformulated this problem in the context of hierarchical convolutional neural networks (CNNs)—whose architectures have been inspired by the hierarchical signal processing of the mammalian visual system—and examined perceptual stability as an optimization process that identifies image-defining features for accurate image classification in the presence of movements. Movement signals, multiplexed with visual inputs along overlapping convolutional layers, aided classification invariance of shifted images by making the classification faster to learn and more robust relative to input noise. Classification invariance was reflected in activity manifolds associated with image categories emerging in late CNN layers and with network units acquiring movement-associated activity modulations as observed experimentally during saccadic eye movements. Our findings provide a computational framework that unifies a multitude of biological observations on perceptual stability under optimality principles for image classification in artificial neural networks. Stable visual perception during eye and body movements suggests neural algorithms that convert location information—"where” type of signals—across multiple frames of reference, for instance, from retinocentric to craniocentric coordinates. Accordingly, numerous theoretical studies have proposed biologically plausible computational processes to achieve such transformations. However, how coordinate transformations can then be used by the hierarchy of cortical visual areas to produce stable perception remains largely unknown. Here, we explore the hypothesis that perception equates to the activity states of networks trained to classify “features” (e.g., objects, salient components) in the visual scene, and perceptual stability equates to robust classification of these features relative to self-generated movements, that is, a “what” type of information processing. We demonstrate in CNNs that neural signals related to eye and body movements support accurate image classification by making “where” type of computations—localization invariances—faster to learn and more robust relative to input perturbations. Therefore, by equating perception to the activity states of classifier networks, we provide a simple unifying mechanistic framework to explain the role movement signals in support of stable perception in dynamic interactions with the environment.
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3
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Silva AE, Tsang K, Hasan SJ, Thompson B. Precise oculocentric mapping of transcranial magnetic stimulation-evoked phosphenes. Neuroreport 2021; 32:913-917. [PMID: 34102648 PMCID: PMC8253501 DOI: 10.1097/wnr.0000000000001683] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 05/10/2021] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Transcranial magnetic stimulation (TMS)-evoked phosphenes are oculocentric; their perceived location depends upon eye position. We investigated the accuracy and precision of TMS-evoked phosphene oculocentric mapping. METHODS We evoked central phosphenes by stimulating early visual cortical areas with TMS, systematically examining the effect of eye position by asking participants to report the location of the evoked phosphene. We tested whether any systematic differences in the precision or accuracy of responses occurred as a function of eye position. RESULTS Perceived phosphene locations map veridically to eye position, although there are considerable individual differences in the reliability of this mapping. CONCLUSIONS Our results emphasize the need to carefully control eye movements when carrying out phosphene localization studies and suggest that individual differences in the reliability of the reported position of individual phosphenes must be considered.
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Affiliation(s)
- Andrew E. Silva
- School of Optometry and Vision Science, University of Waterloo, Waterloo, Canada
| | - Katelyn Tsang
- School of Optometry and Vision Science, University of Waterloo, Waterloo, Canada
| | - Syeda Javeria Hasan
- School of Optometry and Vision Science, University of Waterloo, Waterloo, Canada
| | - Benjamin Thompson
- School of Optometry and Vision Science, University of Waterloo, Waterloo, Canada
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4
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Allison-Walker T, Hagan MA, Price NSC, Wong YT. Microstimulation-evoked neural responses in visual cortex are depth dependent. Brain Stimul 2021; 14:741-750. [PMID: 33975054 DOI: 10.1016/j.brs.2021.04.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 02/26/2021] [Accepted: 04/27/2021] [Indexed: 10/21/2022] Open
Abstract
BACKGROUND Cortical visual prostheses often use penetrating electrode arrays to deliver microstimulation to the visual cortex. To optimize electrode placement within the cortex, the neural responses to microstimulation at different cortical depths must first be understood. OBJECTIVE We investigated how the neural responses evoked by microstimulation in cortex varied with cortical depth, of both stimulation and response. METHODS A 32-channel single shank electrode array was inserted into the primary visual cortex of anaesthetized rats, such that it spanned all cortical layers. Microstimulation with currents up to 14 μA (single biphasic pulse, 200 μs per phase) was applied at depths spanning 1600 μm, while simultaneously recording neural activity on all channels within a response window 2.25-11 ms. RESULTS Stimulation elicited elevated neuronal firing rates at all depths of cortex. Compared to deep sites, superficial stimulation sites responded with higher firing rates at a given current and had lower thresholds. The laminar spread of evoked activity across cortical depth depended on stimulation depth, in line with anatomical models. CONCLUSION Stimulation in the superficial layers of visual cortex evokes local neural activity with the lowest thresholds, and stimulation in the deep layers evoked the most activity across the cortical column. In conjunction with perceptual reports, these data suggest that the optimal electrode placement for cortical microstimulation prostheses has electrodes positioned in layers 2/3, and at the top of layer 5.
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Affiliation(s)
- Tim Allison-Walker
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic, 3800, Australia; ARC Centre of Excellence for Integrative Brain Function, Australia; Monash Vision Group, Monash University, Clayton, Vic, 3800, Australia
| | - Maureen A Hagan
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic, 3800, Australia; ARC Centre of Excellence for Integrative Brain Function, Australia
| | - Nicholas S C Price
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic, 3800, Australia; ARC Centre of Excellence for Integrative Brain Function, Australia
| | - Yan T Wong
- Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Vic, 3800, Australia; ARC Centre of Excellence for Integrative Brain Function, Australia; Department of Electrical and Computer Systems Engineering, Monash University, Clayton, Vic, 3800, Australia; Monash Vision Group, Monash University, Clayton, Vic, 3800, Australia.
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5
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Hafed ZM, Yoshida M, Tian X, Buonocore A, Malevich T. Dissociable Cortical and Subcortical Mechanisms for Mediating the Influences of Visual Cues on Microsaccadic Eye Movements. Front Neural Circuits 2021; 15:638429. [PMID: 33776656 PMCID: PMC7991613 DOI: 10.3389/fncir.2021.638429] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Accepted: 02/22/2021] [Indexed: 12/13/2022] Open
Abstract
Visual selection in primates is intricately linked to eye movements, which are generated by a network of cortical and subcortical neural circuits. When visual selection is performed covertly, without foveating eye movements toward the selected targets, a class of fixational eye movements, called microsaccades, is still involved. Microsaccades are small saccades that occur when maintaining precise gaze fixation on a stationary point, and they exhibit robust modulations in peripheral cueing paradigms used to investigate covert visual selection mechanisms. These modulations consist of changes in both microsaccade directions and frequencies after cue onsets. Over the past two decades, the properties and functional implications of these modulations have been heavily studied, revealing a potentially important role for microsaccades in mediating covert visual selection effects. However, the neural mechanisms underlying cueing effects on microsaccades are only beginning to be investigated. Here we review the available causal manipulation evidence for these effects' cortical and subcortical substrates. In the superior colliculus (SC), activity representing peripheral visual cues strongly influences microsaccade direction, but not frequency, modulations. In the cortical frontal eye fields (FEF), activity only compensates for early reflexive effects of cues on microsaccades. Using evidence from behavior, theoretical modeling, and preliminary lesion data from the primary visual cortex and microstimulation data from the lower brainstem, we argue that the early reflexive microsaccade effects arise subcortically, downstream of the SC. Overall, studying cueing effects on microsaccades in primates represents an important opportunity to link perception, cognition, and action through unaddressed cortical-subcortical neural interactions. These interactions are also likely relevant in other sensory and motor modalities during other active behaviors.
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Affiliation(s)
- Ziad M. Hafed
- Physiology of Active Vision Laboratory, Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany
- Hertie Institute for Clinical Brain Research, Tübingen University, Tübingen, Germany
| | - Masatoshi Yoshida
- Center for Human Nature, Artificial Intelligence, and Neuroscience, Hokkaido University, Sapporo, Japan
| | - Xiaoguang Tian
- Department of Neurobiology, University of Pittsburgh Brain Institute, University of Pittsburgh, Pittsburgh, PA, United States
| | - Antimo Buonocore
- Physiology of Active Vision Laboratory, Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany
- Hertie Institute for Clinical Brain Research, Tübingen University, Tübingen, Germany
| | - Tatiana Malevich
- Physiology of Active Vision Laboratory, Werner Reichardt Centre for Integrative Neuroscience, Tübingen University, Tübingen, Germany
- Hertie Institute for Clinical Brain Research, Tübingen University, Tübingen, Germany
- Graduate School of Neural and Behavioural Sciences, International Max-Planck Research School, Tübingen University, Tübingen, Germany
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6
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Davis ZW, Muller L, Martinez-Trujillo J, Sejnowski T, Reynolds JH. Spontaneous travelling cortical waves gate perception in behaving primates. Nature 2020; 587:432-436. [PMID: 33029013 PMCID: PMC7677221 DOI: 10.1038/s41586-020-2802-y] [Citation(s) in RCA: 85] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 07/10/2020] [Indexed: 01/20/2023]
Abstract
Perceptual sensitivity varies from moment to moment. One potential source of variability is spontaneous fluctuations in cortical activity that can travel as a wave1. Spontaneous traveling waves have been reported during anesthesia2–7, but it is not known whether spontaneous traveling waves play a role during waking perception. Using newly developed analytic techniques to characterize the moment-to-moment dynamics of noisy multielectrode data, we find spontaneous waves of activity in extrastriate visual cortex of awake, behaving marmosets (Callithrix jacchus). In monkeys trained to detect faint visual targets, the timing and position of spontaneous traveling waves, prior to target onset, predict the magnitude of target-evoked activity and the likelihood of target detection. In contrast, spatially disorganized fluctuations of neural activity are much less predictive. These results reveal an important role for spontaneous traveling waves in sensory processing through modulating neural and perceptual sensitivity.
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Affiliation(s)
- Zachary W Davis
- The Salk Institute for Biological Studies, La Jolla, CA, USA.
| | - Lyle Muller
- The Salk Institute for Biological Studies, La Jolla, CA, USA.,Department of Applied Mathematics, Western University, London, Ontario, Canada.,Robarts Research and Brain and Mind Institute, Western University, London, Ontario, Canada.,Institut de Neurosciences de la Timone (INT), UMR7289, CNRS, Aix-Marseille Université, Marseille, France
| | - Julio Martinez-Trujillo
- Robarts Research and Brain and Mind Institute, Western University, London, Ontario, Canada.,Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.,Department of Psychiatry, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
| | | | - John H Reynolds
- The Salk Institute for Biological Studies, La Jolla, CA, USA.
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Roe AW, Chen G, Xu AG, Hu J. A roadmap to a columnar visual cortical prosthetic. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2020.06.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Andelman-Gur MM, Gazit T, Andelman F, Kipervasser S, Kramer U, Neufeld MY, Fried I, Fahoum F. Spatial distribution and hemispheric asymmetry of electrically evoked experiential phenomena in the human brain. J Neurosurg 2020; 133:54-62. [PMID: 31200379 DOI: 10.3171/2019.3.jns183429] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 03/24/2019] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Experiential phenomena (EP), such as illusions and complex hallucinations, are vivid experiences created in one's mind. They can occur spontaneously as epileptic auras or can be elicited by electrical brain stimulation (EBS) in patients undergoing presurgical evaluation for drug-resistant epilepsy. Previous work suggests that EP arise from activation of different nodes within interconnected neural networks mainly in the temporal lobes. Yet, the anatomical extent of these neural networks has not been described and the question of lateralization of EP has not been fully addressed. To this end, an extended number of brain regions in which electrical stimulation elicited EP were studied to test whether there is a lateralization propensity to EP phenomena. METHODS A total of 19 drug-resistant focal epilepsy patients who underwent EBS as part of invasive presurgical evaluation and who experienced EP during the stimulation were included. Spatial dispersion of visual and auditory illusions and complex hallucinations in each hemisphere was determined by calculation of Euclidean distances between electrodes and their centroid in common space, based on (x, y, z) Cartesian coordinates of electrode locations. RESULTS In total, 5857 stimulation epochs were analyzed; 917 stimulations elicited responses, out of which 130 elicited EP. Complex visual hallucinations were found to be widely dispersed in the right hemisphere, while they were tightly clustered in the occipital lobe of the left hemisphere. Visual illusions were elicited mostly in the occipital lobes bilaterally. Auditory illusions and hallucinations were evoked symmetrically in the temporal lobes. CONCLUSIONS These findings suggest that complex visual hallucinations arise from wider spread in the right compared to the left hemisphere, possibly mirroring the asymmetry in the white matter organization of the two hemispheres. These results offer some insights into lateralized differences in functional organization and connectivity that may be important for functional mapping and planning of surgical resections in patients with epilepsy.
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Affiliation(s)
| | | | | | - Svetlana Kipervasser
- 1Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
- 4Epilepsy and EEG Unit, and
| | - Uri Kramer
- 1Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
- 5Pediatric Epilepsy Unit, Tel Aviv Medical Center, Tel Aviv, Israel; and
| | - Miri Y Neufeld
- 1Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
- 4Epilepsy and EEG Unit, and
| | - Itzhak Fried
- 1Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
- 3Functional Neurosurgery Unit
- 6Department of Neurosurgery, University of California, Los Angeles, California
| | - Firas Fahoum
- 1Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
- 4Epilepsy and EEG Unit, and
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9
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Hu JM, Qian MZ, Tanigawa H, Song XM, Roe AW. Focal Electrical Stimulation of Cortical Functional Networks. Cereb Cortex 2020; 30:5532-5543. [PMID: 32483588 DOI: 10.1093/cercor/bhaa136] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 03/30/2020] [Accepted: 04/27/2020] [Indexed: 01/11/2023] Open
Abstract
Abstract
Traditional electrical stimulation of brain tissue typically affects relatively large volumes of tissue spanning multiple millimeters. This low spatial resolution stimulation results in nonspecific functional effects. In addition, a primary shortcoming of these designs was the failure to take advantage of inherent functional organization in the cerebral cortex. Here, we describe a new method to electrically stimulate the brain which achieves selective targeting of single feature-specific domains in visual cortex. We provide evidence that this paradigm achieves mesoscale, functional network-specificity, and intensity dependence in a way that mimics visual stimulation. Application of this approach to known feature domains (such as color, orientation, motion, and depth) in visual cortex may lead to important functional improvements in the specificity and sophistication of brain stimulation methods and has implications for visual cortical prosthetic design.
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Affiliation(s)
- Jia Ming Hu
- Department of Neurology of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, School of Medicine, Zhejiang University, Hangzhou 310029, China
| | - Mei Zhen Qian
- Department of Neurology of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, School of Medicine, Zhejiang University, Hangzhou 310029, China
| | - Hisashi Tanigawa
- Department of Neurology of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, School of Medicine, Zhejiang University, Hangzhou 310029, China
| | - Xue Mei Song
- Department of Neurology of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, School of Medicine, Zhejiang University, Hangzhou 310029, China
| | - Anna Wang Roe
- Department of Neurology of the Second Affiliated Hospital, Interdisciplinary Institute of Neuroscience and Technology, School of Medicine, Zhejiang University, Hangzhou 310029, China
- Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang University, Hangzhou, Hangzhou 310029, China
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR 97006 USA
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10
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Tanaka Y, Nomoto T, Shiki T, Sakata Y, Shimada Y, Hayashida Y, Yagi T. Focal activation of neuronal circuits induced by microstimulation in the visual cortex. J Neural Eng 2019; 16:036007. [PMID: 30818288 DOI: 10.1088/1741-2552/ab0b80] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Microstimulation to the cortical tissue applied with penetrating electrodes delivers current that spreads concentrically around the electrode tip and is known to evoke focal visual sensations, i.e. phosphenes. However, to date, there is no direct evidence depicting the spatiotemporal properties of neuronal activity induced immediately after microstimulation and how such activity drives the subsequent local cortical circuits. APPROACH In the present study, we imaged the spatiotemporal distribution of action potentials (APs) directly induced by microstimulation and the subsequent trans-synaptic signal propagation using a voltage-sensitive dye (VSD) and a calcium-sensitive dye (CaSD) in slice preparations of the mouse primary visual cortex. MAIN RESULTS The directly induced APs were confined to the close vicinity of the electrode tip, and the effective distance of excitation was proportional to the square root of the current intensity. The excitation around the electrode tip in layer IV mainly propagated to layer II/III to further induce the subsequent focal activation in downstream local cortical circuits. The extent of activation in the downstream circuits was restrained by competitive interactions between excitatory and inhibitory signals. Namely, the spread of the excitation to lateral neighbor neurons along the layer II/III was confined by the delayed inhibition that also spread laterally at a faster rate. SIGNIFICANCE These observations indicate that dynamic interactions between excitatory and inhibitory signals play a critical role in the focal activation of a cortical circuit in response to intracortical microstimulation and, therefore, in evoking a localized phosphene.
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Affiliation(s)
- Yuta Tanaka
- Division of Electrical, Electronic, and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
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Aberra AS, Peterchev AV, Grill WM. Biophysically realistic neuron models for simulation of cortical stimulation. J Neural Eng 2018; 15:066023. [PMID: 30127100 PMCID: PMC6239949 DOI: 10.1088/1741-2552/aadbb1] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
OBJECTIVE We implemented computational models of human and rat cortical neurons for simulating the neural response to cortical stimulation with electromagnetic fields. APPROACH We adapted model neurons from the library of Blue Brain models to reflect biophysical and geometric properties of both adult rat and human cortical neurons and coupled the model neurons to exogenous electric fields (E-fields). The models included 3D reconstructed axonal and dendritic arbors, experimentally-validated electrophysiological behaviors, and multiple, morphological variants within cell types. Using these models, we characterized the single-cell responses to intracortical microstimulation (ICMS) and uniform E-field with dc as well as pulsed currents. MAIN RESULTS The strength-duration and current-distance characteristics of the model neurons to ICMS agreed with published experimental results, as did the subthreshold polarization of cell bodies and axon terminals by uniform dc E-fields. For all forms of stimulation, the lowest threshold elements were terminals of the axon collaterals, and the dependence of threshold and polarization on spatial and temporal stimulation parameters was strongly affected by morphological features of the axonal arbor, including myelination, diameter, and branching. SIGNIFICANCE These results provide key insights into the mechanisms of cortical stimulation. The presented models can be used to study various cortical stimulation modalities while incorporating detailed spatial and temporal features of the applied E-field.
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Affiliation(s)
- Aman S Aberra
- Department of Biomedical Engineering, School of Engineering, Duke University, Durham, NC 27710, United States of America
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12
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Spatio-temporal characteristics of population responses evoked by microstimulation in the barrel cortex. Sci Rep 2018; 8:13913. [PMID: 30224723 PMCID: PMC6141467 DOI: 10.1038/s41598-018-32148-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 09/03/2018] [Indexed: 11/09/2022] Open
Abstract
Intra-cortical microstimulation (ICMS) is a widely used technique to artificially stimulate cortical tissue. This method revealed functional maps and provided causal links between neuronal activity and cognitive, sensory or motor functions. The effects of ICMS on neural activity depend on stimulation parameters. Past studies investigated the effects of stimulation frequency mainly at the behavioral or motor level. Therefore the direct effect of frequency stimulation on the evoked spatio-temporal patterns of cortical activity is largely unknown. To study this question we used voltage-sensitive dye imaging to measure the population response in the barrel cortex of anesthetized rats evoked by high frequency stimulation (HFS), a lower frequency stimulation (LFS) of the same duration or a single pulse stimulation. We found that single pulse and short trains of ICMS induced cortical activity extending over few mm. HFS evoked a lower population response during the sustained response and showed a smaller activation across time and space compared with LFS. Finally the evoked population response started near the electrode site and spread horizontally at a propagation velocity in accordance with horizontal connections. In summary, HFS was less effective in cortical activation compared to LFS although HFS had 5 fold more energy than LFS.
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Najarpour Foroushani A, Pack CC, Sawan M. Cortical visual prostheses: from microstimulation to functional percept. J Neural Eng 2018; 15:021005. [DOI: 10.1088/1741-2552/aaa904] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Bosking WH, Beauchamp MS, Yoshor D. Electrical Stimulation of Visual Cortex: Relevance for the Development of Visual Cortical Prosthetics. Annu Rev Vis Sci 2017; 3:141-166. [PMID: 28753382 PMCID: PMC6916716 DOI: 10.1146/annurev-vision-111815-114525] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Electrical stimulation of the cerebral cortex is a powerful tool for exploring cortical function. Stimulation of early visual cortical areas is easily detected by subjects and produces simple visual percepts known as phosphenes. A device implanted in visual cortex that generates patterns of phosphenes could be used as a substitute for natural vision in blind patients. We review the possibilities and limitations of such a device, termed a visual cortical prosthetic. Currently, we can predict the location and size of phosphenes produced by stimulation of single electrodes. A functional prosthetic, however, must produce spatial temporal patterns of activity that will result in the perception of complex visual objects. Although stimulation of later visual cortical areas alone usually does not lead to a visual percept, it can alter visual perception and the performance of visual behaviors, and training subjects to use signals injected into these areas may be possible.
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Affiliation(s)
- William H Bosking
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030; , ,
| | - Michael S Beauchamp
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030; , ,
| | - Daniel Yoshor
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030; , ,
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Saturation in Phosphene Size with Increasing Current Levels Delivered to Human Visual Cortex. J Neurosci 2017; 37:7188-7197. [PMID: 28652411 DOI: 10.1523/jneurosci.2896-16.2017] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 05/19/2017] [Accepted: 05/25/2017] [Indexed: 11/21/2022] Open
Abstract
Electrically stimulating early visual cortex results in a visual percept known as a phosphene. Although phosphenes can be evoked by a wide range of electrode sizes and current amplitudes, they are invariably described as small. To better understand this observation, we electrically stimulated 93 electrodes implanted in the visual cortex of 13 human subjects who reported phosphene size while stimulation current was varied. Phosphene size increased as the stimulation current was initially raised above threshold, but then rapidly reached saturation. Phosphene size also depended on the location of the stimulated site, with size increasing with distance from the foveal representation. We developed a model relating phosphene size to the amount of activated cortex and its location within the retinotopic map. First, a sigmoidal curve was used to predict the amount of activated cortex at a given current. Second, the amount of active cortex was converted to degrees of visual angle by multiplying by the inverse cortical magnification factor for that retinotopic location. This simple model accurately predicted phosphene size for a broad range of stimulation currents and cortical locations. The unexpected saturation in phosphene sizes suggests that the functional architecture of cerebral cortex may impose fundamental restrictions on the spread of artificially evoked activity and this may be an important consideration in the design of cortical prosthetic devices.SIGNIFICANCE STATEMENT Understanding the neural basis for phosphenes, the visual percepts created by electrical stimulation of visual cortex, is fundamental to the development of a visual cortical prosthetic. Our experiments in human subjects implanted with electrodes over visual cortex show that it is the activity of a large population of cells spread out across several millimeters of tissue that supports the perception of a phosphene. In addition, we describe an important feature of the production of phosphenes by electrical stimulation: phosphene size saturates at a relatively low current level. This finding implies that, with current methods, visual prosthetics will have a limited dynamic range available to control the production of spatial forms and that more advanced stimulation methods may be required.
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Overstreet CK, Hellman RB, Ponce Wong RD, Santos VJ, Helms Tillery SI. Discriminability of Single and Multichannel Intracortical Microstimulation within Somatosensory Cortex. Front Bioeng Biotechnol 2016; 4:91. [PMID: 27995126 PMCID: PMC5133427 DOI: 10.3389/fbioe.2016.00091] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 11/14/2016] [Indexed: 11/13/2022] Open
Abstract
The addition of tactile and proprioceptive feedback to neuroprosthetic limbs is expected to significantly improve the control of these devices. Intracortical microstimulation (ICMS) of somatosensory cortex is a promising method of delivering this sensory feedback. To date, the main focus of somatosensory ICMS studies has been to deliver discriminable signals, corresponding to varying intensity, to a single location in cortex. However, multiple independent and simultaneous streams of sensory information will need to be encoded by ICMS to provide functionally relevant feedback for a neuroprosthetic limb (e.g., encoding contact events and pressure on multiple digits). In this study, we evaluated the ability of an awake, behaving non-human primate (Macaca mulatta) to discriminate ICMS stimuli delivered on multiple electrodes spaced within somatosensory cortex. We delivered serial stimulation on single electrodes to evaluate the discriminability of sensations corresponding to ICMS of distinct cortical locations. Additionally, we delivered trains of multichannel stimulation, derived from a tactile sensor, synchronously across multiple electrodes. Our results indicate that discrimination of multiple ICMS stimuli is a challenging task, but that discriminable sensory percepts can be elicited by both single and multichannel ICMS on electrodes spaced within somatosensory cortex.
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Affiliation(s)
- Cynthia K Overstreet
- SensoriMotor Research Group, School of Biological and Health Systems Engineering, Arizona State University , Tempe, AZ , USA
| | - Randall B Hellman
- Biomechatronics Lab, Department of Mechanical and Aerospace Engineering, Arizona State University , Tempe, AZ , USA
| | - Ruben D Ponce Wong
- Biomechatronics Lab, Department of Mechanical and Aerospace Engineering, Arizona State University , Tempe, AZ , USA
| | - Veronica J Santos
- Biomechatronics Lab, Department of Mechanical and Aerospace Engineering, Arizona State University , Tempe, AZ , USA
| | - Stephen I Helms Tillery
- SensoriMotor Research Group, School of Biological and Health Systems Engineering, Arizona State University , Tempe, AZ , USA
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Kristjánsson Á, Moldoveanu A, Jóhannesson ÓI, Balan O, Spagnol S, Valgeirsdóttir VV, Unnthorsson R. Designing sensory-substitution devices: Principles, pitfalls and potential1. Restor Neurol Neurosci 2016; 34:769-87. [PMID: 27567755 PMCID: PMC5044782 DOI: 10.3233/rnn-160647] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
An exciting possibility for compensating for loss of sensory function is to augment deficient senses by conveying missing information through an intact sense. Here we present an overview of techniques that have been developed for sensory substitution (SS) for the blind, through both touch and audition, with special emphasis on the importance of training for the use of such devices, while highlighting potential pitfalls in their design. One example of a pitfall is how conveying extra information about the environment risks sensory overload. Related to this, the limits of attentional capacity make it important to focus on key information and avoid redundancies. Also, differences in processing characteristics and bandwidth between sensory systems severely constrain the information that can be conveyed. Furthermore, perception is a continuous process and does not involve a snapshot of the environment. Design of sensory substitution devices therefore requires assessment of the nature of spatiotemporal continuity for the different senses. Basic psychophysical and neuroscientific research into representations of the environment and the most effective ways of conveying information should lead to better design of sensory substitution systems. Sensory substitution devices should emphasize usability, and should not interfere with other inter- or intramodal perceptual function. Devices should be task-focused since in many cases it may be impractical to convey too many aspects of the environment. Evidence for multisensory integration in the representation of the environment suggests that researchers should not limit themselves to a single modality in their design. Finally, we recommend active training on devices, especially since it allows for externalization, where proximal sensory stimulation is attributed to a distinct exterior object.
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Affiliation(s)
- Árni Kristjánsson
- Laboratory of Visual Perception and Visuomotor control, University of Iceland, Faculty of Psychology, School of Health Sciences, Reykjavik, Iceland
| | - Alin Moldoveanu
- University Politehnica of Bucharest, Faculty of Automatic Control and Computers, Computer Science and Engineering Department, Bucharest, Romania
| | - Ómar I. Jóhannesson
- Laboratory of Visual Perception and Visuomotor control, University of Iceland, Faculty of Psychology, School of Health Sciences, Reykjavik, Iceland
| | - Oana Balan
- University Politehnica of Bucharest, Faculty of Automatic Control and Computers, Computer Science and Engineering Department, Bucharest, Romania
| | - Simone Spagnol
- Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, School of Engineering and Natural Sciences, Reykjavik, Iceland
| | - Vigdís Vala Valgeirsdóttir
- Laboratory of Visual Perception and Visuomotor control, University of Iceland, Faculty of Psychology, School of Health Sciences, Reykjavik, Iceland
| | - Rúnar Unnthorsson
- Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, School of Engineering and Natural Sciences, Reykjavik, Iceland
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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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Stephani C, Koubeissi M. Differences of Intracranial Electrical Stimulation Thresholds in the Human Brain. Brain Stimul 2015; 8:724-9. [DOI: 10.1016/j.brs.2015.02.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 02/27/2015] [Indexed: 12/01/2022] Open
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Dagnino B, Gariel-Mathis MA, Roelfsema PR. Microstimulation of area V4 has little effect on spatial attention and on perception of phosphenes evoked in area V1. J Neurophysiol 2014; 113:730-9. [PMID: 25392172 DOI: 10.1152/jn.00645.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Previous transcranial magnetic stimulation (TMS) studies suggested that feedback from higher to lower areas of the visual cortex is important for the access of visual information to awareness. However, the influence of cortico-cortical feedback on awareness and the nature of the feedback effects are not yet completely understood. In the present study, we used electrical microstimulation in the visual cortex of monkeys to test the hypothesis that cortico-cortical feedback plays a role in visual awareness. We investigated the interactions between the primary visual cortex (V1) and area V4 by applying microstimulation in both cortical areas at various delays. We report that the monkeys detected the phosphenes produced by V1 microstimulation but subthreshold V4 microstimulation did not influence V1 phosphene detection thresholds. A second experiment examined the influence of V4 microstimulation on the monkeys' ability to detect the dimming of one of three peripheral visual stimuli. Again, microstimulation of a group of V4 neurons failed to modulate the monkeys' perception of a stimulus in their receptive field. We conclude that conditions exist where microstimulation of area V4 has only a limited influence on visual perception.
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Affiliation(s)
- Bruno Dagnino
- Department of Vision and Cognition, Netherlands Institute for Neuroscience (an institute of the Royal Academy of Arts and Sciences of the Netherlands), Amsterdam, The Netherlands
| | - Marie-Alice Gariel-Mathis
- Department of Vision and Cognition, Netherlands Institute for Neuroscience (an institute of the Royal Academy of Arts and Sciences of the Netherlands), Amsterdam, The Netherlands
| | - Pieter R Roelfsema
- Department of Vision and Cognition, Netherlands Institute for Neuroscience (an institute of the Royal Academy of Arts and Sciences of the Netherlands), Amsterdam, The Netherlands; Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, The Netherlands; and Psychiatry Department, Academic Medical Center, Amsterdam, The Netherlands
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Born RT, Trott AR, Hartmann TS. Cortical magnification plus cortical plasticity equals vision? Vision Res 2014; 111:161-9. [PMID: 25449335 DOI: 10.1016/j.visres.2014.10.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 09/15/2014] [Accepted: 10/06/2014] [Indexed: 10/24/2022]
Abstract
Most approaches to visual prostheses have focused on the retina, and for good reasons. The earlier that one introduces signals into the visual system, the more one can take advantage of its prodigious computational abilities. For methods that make use of microelectrodes to introduce electrical signals, however, the limited density and volume occupying nature of the electrodes place severe limits on the image resolution that can be provided to the brain. In this regard, non-retinal areas in general, and the primary visual cortex in particular, possess one large advantage: "magnification factor" (MF)-a value that represents the distance across a sheet of neurons that represents a given angle of the visual field. In the foveal representation of primate primary visual cortex, the MF is enormous-on the order of 15-20 mm/deg in monkeys and humans, whereas on the retina, the MF is limited by the optical design of the eye to around 0.3m m/deg. This means that, for an electrode array of a given density, a much higher-resolution image can be introduced into V1 than onto the retina (or any other visual structure). In addition to this tremendous advantage in resolution, visual cortex is plastic at many different levels ranging from a very local ability to learn to better detect electrical stimulation to higher levels of learning that permit human observers to adapt to radical changes to their visual inputs. We argue that the combination of the large magnification factor and the impressive ability of the cerebral cortex to learn to recognize arbitrary patterns, might outweigh the disadvantages of bypassing earlier processing stages and makes V1 a viable option for the restoration of vision.
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Affiliation(s)
- Richard T Born
- Dept. of Neurobiology, Harvard Medical School, United States; Center for Brain Science, Harvard University, United States.
| | - Alexander R Trott
- Dept. of Neurobiology, Harvard Medical School, United States; Harvard PhD Program in Neuroscience, United States.
| | - Till S Hartmann
- Dept. of Neurobiology, Harvard Medical School, United States.
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Dopamine-modulated recurrent corticoefferent feedback in primary sensory cortex promotes detection of behaviorally relevant stimuli. J Neurosci 2014; 34:1234-47. [PMID: 24453315 DOI: 10.1523/jneurosci.1990-13.2014] [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] [Indexed: 01/14/2023] Open
Abstract
Dopaminergic neurotransmission in primary auditory cortex (AI) has been shown to be involved in learning and memory functions. Moreover, dopaminergic projections and D1/D5 receptor distributions display a layer-dependent organization, suggesting specific functions in the cortical circuitry. However, the circuit effects of dopaminergic neurotransmission in sensory cortex and their possible roles in perception, learning, and memory are largely unknown. Here, we investigated layer-specific circuit effects of dopaminergic neuromodulation using current source density (CSD) analysis in AI of Mongolian gerbils. Pharmacological stimulation of D1/D5 receptors increased auditory-evoked synaptic currents in infragranular layers, prolonging local thalamocortical input via positive feedback between infragranular output and granular input. Subsequently, dopamine promoted sustained cortical activation by prolonged recruitment of long-range corticocortical networks. A detailed circuit analysis combining layer-specific intracortical microstimulation (ICMS), CSD analysis, and pharmacological cortical silencing revealed that cross-laminar feedback enhanced by dopamine relied on a positive, fast-acting recurrent corticoefferent loop, most likely relayed via local thalamic circuits. Behavioral signal detection analysis further showed that activation of corticoefferent output by infragranular ICMS, which mimicked auditory activation under dopaminergic influence, was most effective in eliciting a behaviorally detectable signal. Our results show that D1/D5-mediated dopaminergic modulation in sensory cortex regulates positive recurrent corticoefferent feedback, which enhances states of high, persistent activity in sensory cortex evoked by behaviorally relevant stimuli. In boosting horizontal network interactions, this potentially promotes the readout of task-related information from cortical synapses and improves behavioral stimulus detection.
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Overstreet CK, Klein JD, Helms Tillery SI. Computational modeling of direct neuronal recruitment during intracortical microstimulation in somatosensory cortex. J Neural Eng 2013; 10:066016. [PMID: 24280531 DOI: 10.1088/1741-2560/10/6/066016] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
OBJECTIVE Electrical stimulation of cortical tissue could be used to deliver sensory information as part of a neuroprosthetic device, but current control of the location, resolution, quality, and intensity of sensations elicited by intracortical microstimulation (ICMS) remains inadequate for this purpose. One major obstacle to resolving this problem is the poor understanding of the neural activity induced by ICMS. Even with new imaging methods, quantifying the activity of many individual neurons within cortex is difficult. APPROACH We used computational modeling to examine the response of somatosensory cortex to ICMS. We modeled the axonal arbors of eight distinct morphologies of interneurons and seven types of pyramidal neurons found in somatosensory cortex and identified their responses to extracellular stimulation. We then combined these axonal elements to form a multi-layered slab of simulated cortex and investigated the patterns of neural activity directly induced by ICMS. Specifically we estimated the number, location, and variety of neurons directly recruited by stimulation on a single penetrating microelectrode. MAIN RESULTS The population of neurons activated by ICMS was dependent on both stimulation strength and the depth of the electrode within cortex. Strikingly, stimulation recruited interneurons and pyramidal neurons in very different patterns. Interneurons are primarily recruited within a dense, continuous region around the electrode, while pyramidal neurons were recruited in a sparse fashion both near the electrode and up to several millimeters away. Thus ICMS can lead to an unexpectedly complex spatial distribution of firing neurons. SIGNIFICANCE These results lend new insights to the complexity and range of neural activity that can be induced by ICMS. This work also suggests mechanisms potentially responsible for the inconsistency and unnatural quality of sensations initiated by ICMS. Understanding these mechanisms will aid in the design of stimulation that can be used to generate effective sensory feedback for neuroprosthetic devices.
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Affiliation(s)
- C K Overstreet
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85287, USA
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Restoring the sense of touch with a prosthetic hand through a brain interface. Proc Natl Acad Sci U S A 2013; 110:18279-84. [PMID: 24127595 DOI: 10.1073/pnas.1221113110] [Citation(s) in RCA: 175] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Our ability to manipulate objects dexterously relies fundamentally on sensory signals originating from the hand. To restore motor function with upper-limb neuroprostheses requires that somatosensory feedback be provided to the tetraplegic patient or amputee. Given the complexity of state-of-the-art prosthetic limbs and, thus, the huge state space they can traverse, it is desirable to minimize the need for the patient to learn associations between events impinging on the limb and arbitrary sensations. Accordingly, we have developed approaches to intuitively convey sensory information that is critical for object manipulation--information about contact location, pressure, and timing--through intracortical microstimulation of primary somatosensory cortex. In experiments with nonhuman primates, we show that we can elicit percepts that are projected to a localized patch of skin and that track the pressure exerted on the skin. In a real-time application, we demonstrate that animals can perform a tactile discrimination task equally well whether mechanical stimuli are delivered to their native fingers or to a prosthetic one. Finally, we propose that the timing of contact events can be signaled through phasic intracortical microstimulation at the onset and offset of object contact that mimics the ubiquitous on and off responses observed in primary somatosensory cortex to complement slowly varying pressure-related feedback. We anticipate that the proposed biomimetic feedback will considerably increase the dexterity and embodiment of upper-limb neuroprostheses and will constitute an important step in restoring touch to individuals who have lost it.
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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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26
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Tehovnik E, Slocum W. Two-photon imaging and the activation of cortical neurons. Neuroscience 2013; 245:12-25. [DOI: 10.1016/j.neuroscience.2013.04.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 02/22/2013] [Accepted: 04/10/2013] [Indexed: 10/26/2022]
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Interdisciplinary implications on autism, savantism, Asperger syndrome and the biophysical picture representation: Thinking in pictures. COGN SYST RES 2013. [DOI: 10.1016/j.cogsys.2012.05.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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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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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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Synchronization Across Sensory Cortical Areas by Electrical Microstimulation is Sufficient for Behavioral Discrimination. Cereb Cortex 2012; 23:2976-86. [DOI: 10.1093/cercor/bhs288] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Bókkon I, Salari V. Hypothesis about brilliant lights by bioluminescent photons in near death experiences. Med Hypotheses 2012; 79:47-9. [PMID: 22543076 DOI: 10.1016/j.mehy.2012.03.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 03/22/2012] [Accepted: 03/30/2012] [Indexed: 10/28/2022]
Abstract
In near death experiences (NDEs), seeing a brilliant light may arise in the recovery period following cardiac arrest, but the subjects can think that these experiences had happened during the actual period itself. Here we hypothesize a biophysical explanation about the encounter with a brilliant light in NDEs. Accordingly, meeting brilliant light in NDEs is due to the reperfusion that induces unregulated overproduction of free radicals and excited biomolecules among them in numerous parts in the visual system. Unregulated free radicals and excited species can produce a transient increase of bioluminescent photons in different areas of the visual system. If this excess of bioluminescent photon emission exceeds a threshold, they can appear as (phosphene) lights in our mind. In other words, seeing a brilliant light in NDEs may due to bioluminescent photons simultaneously generated in the recovery phase of numerous areas of the visual system and the brain interprets these intrinsic bioluminescent photons as if they were originated from the external visual world. Although our biophysical explanation about brilliant light phenomenon in NDEs can be promising, we do not reject further potential notions.
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Affiliation(s)
- István Bókkon
- Doctoral School of Pharmaceutical and Pharmacological Sciences, Semmelweis University, Hungary; Vision Research Institute, 25 Rita Street, Lowell, MA 01854, USA.
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Wang Q, Millard DC, Zheng HJ, Stanley GB. Voltage-sensitive dye imaging reveals improved topographic activation of cortex in response to manipulation of thalamic microstimulation parameters. J Neural Eng 2012; 9:026008. [PMID: 22327024 PMCID: PMC3371357 DOI: 10.1088/1741-2560/9/2/026008] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Voltage-sensitive dye imaging was used to quantify in vivo, network level spatiotemporal cortical activation in response to electrical microstimulation of the thalamus in the rat vibrissa pathway. Thalamic microstimulation evoked a distinctly different cortical response than natural sensory stimulation, with response to microstimulation spreading over a larger area of cortex and being topographically misaligned with the cortical column to which the stimulated thalamic region projects. Electrical stimulation with cathode-leading asymmetric waveforms reduced this topographic misalignment while simultaneously increasing the spatial specificity of the cortical activation. Systematically increasing the asymmetry of the microstimulation pulses revealed a continuum between symmetric and asymmetric stimulation that gradually reduced the topographic bias. These data strongly support the hypothesis that manipulation of the electrical stimulation waveform can be used to selectively activate specific neural elements. Specifically, our results are consistent with the prediction that cathode-leading asymmetric waveforms preferentially stimulate cell bodies over axons, while symmetric waveforms preferentially activate axons over cell bodies. The findings here provide some initial steps toward the design and optimization of microstimulation of neural circuitry, and open the door to more sophisticated engineering tools, such as nonlinear system identification techniques, to develop technologies for more effective control of activity in the nervous system.
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Affiliation(s)
- Qi Wang
- Department of Biomedical Engineering, Georgia Institute of Technology /Emory University, Atlanta, Georgia 30332, USA
| | - Daniel C. Millard
- Department of Biomedical Engineering, Georgia Institute of Technology /Emory University, Atlanta, Georgia 30332, USA
| | - He J.V. Zheng
- Department of Biomedical Engineering, Georgia Institute of Technology /Emory University, Atlanta, Georgia 30332, USA
| | - Garrett B. Stanley
- Department of Biomedical Engineering, Georgia Institute of Technology /Emory University, Atlanta, Georgia 30332, USA
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Sultan F, Augath M, Murayama Y, Tolias AS, Logothetis N. esfMRI of the upper STS: further evidence for the lack of electrically induced polysynaptic propagation of activity in the neocortex. Magn Reson Imaging 2011; 29:1374-81. [DOI: 10.1016/j.mri.2011.04.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 04/04/2011] [Accepted: 04/04/2011] [Indexed: 11/29/2022]
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Collignon O, Champoux F, Voss P, Lepore F. Sensory rehabilitation in the plastic brain. PROGRESS IN BRAIN RESEARCH 2011; 191:211-31. [PMID: 21741554 DOI: 10.1016/b978-0-444-53752-2.00003-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The purpose of this review is to consider new sensory rehabilitation avenues in the context of the brain's remarkable ability to reorganize itself following sensory deprivation. Here, deafness and blindness are taken as two illustrative models. Mainly, two promising rehabilitative strategies based on opposing theoretical principles will be considered: sensory substitution and neuroprostheses. Sensory substitution makes use of the remaining intact senses to provide blind or deaf individuals with coded information of the lost sensory system. This technique thus benefits from added neural resources in the processing of the remaining senses resulting from crossmodal plasticity, which is thought to be coupled with behavioral enhancements in the intact senses. On the other hand, neuroprostheses represent an invasive approach aimed at stimulating the deprived sensory system directly in order to restore, at least partially, its functioning. This technique therefore relies on the neuronal integrity of the brain areas normally dedicated to the deprived sense and is rather hindered by the compensatory reorganization observed in the deprived cortex. Here, we stress that our understanding of the neuroplastic changes that occur in sensory-deprived individuals may help guide the design and the implementation of such rehabilitative methods.
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Affiliation(s)
- Olivier Collignon
- Centre de Recherche en Neuropsychologie et Cognition, CERNEC, Université de Montréal, Montréal, Québec, Canada.
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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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36
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Missimer JH, Seitz RJ, Kleiser R. Data-driven analyses of an fMRI study of a subject experiencing phosphenes. J Magn Reson Imaging 2010; 31:821-8. [PMID: 20373425 DOI: 10.1002/jmri.22122] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To compare two data-driven methods of statistical image analysis, principal and independent component analysis (PCA, ICA), in identifying neural networks related to the transient occurrence of phosphenes experienced by a female patient subsequent to a brain infarct. MATERIALS AND METHODS An initial functional magnetic resonance imaging (fMRI) session consisted of two acquisitions: one of the patient experiencing phosphenes and a second responding to a well-defined visual stimulation paradigm. A second fMRI session 6 months later, when the patient no longer experienced phosphenes, consisted of an acquisition in which no stimulation was presented. Analysis of correlations between the temporal expression coefficients and models of the hemodynamic response identified salient components. Spectral analysis confirmed the identification. The phosphene model was based solely on the subjective report of the patient. RESULTS Both methods revealed occipital cortical and subcortical areas known to be sites for visual information-processing during stimulation, as did SPM. In addition, higher-order visual areas such as the precuneus and the lateral parietal cortex were implicated in the PCA of the phosphenes. CONCLUSION The analyses suggest the capability of data-driven approaches to identify the brain structures involved in these transient, spontaneous visual events.
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Affiliation(s)
- John H Missimer
- Laboratory for Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland.
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Logothetis NK, Augath M, Murayama Y, Rauch A, Sultan F, Goense J, Oeltermann A, Merkle H. The effects of electrical microstimulation on cortical signal propagation. Nat Neurosci 2010; 13:1283-91. [PMID: 20818384 DOI: 10.1038/nn.2631] [Citation(s) in RCA: 233] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Accepted: 08/04/2010] [Indexed: 11/09/2022]
Abstract
Electrical stimulation has been used in animals and humans to study potential causal links between neural activity and specific cognitive functions. Recently, it has found increasing use in electrotherapy and neural prostheses. However, the manner in which electrical stimulation-elicited signals propagate in brain tissues remains unclear. We used combined electrostimulation, neurophysiology, microinjection and functional magnetic resonance imaging (fMRI) to study the cortical activity patterns elicited during stimulation of cortical afferents in monkeys. We found that stimulation of a site in the lateral geniculate nucleus (LGN) increased the fMRI signal in the regions of primary visual cortex (V1) that received input from that site, but suppressed it in the retinotopically matched regions of extrastriate cortex. Consistent with previous observations, intracranial recordings indicated that a short excitatory response occurring immediately after a stimulation pulse was followed by a long-lasting inhibition. Following microinjections of GABA antagonists in V1, LGN stimulation induced positive fMRI signals in all of the cortical areas. Taken together, our findings suggest that electrical stimulation disrupts cortico-cortical signal propagation by silencing the output of any neocortical area whose afferents are electrically stimulated.
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38
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Fridman GY, Blair HT, Blaisdell AP, Judy JW. Perceived intensity of somatosensory cortical electrical stimulation. Exp Brain Res 2010; 203:499-515. [PMID: 20440610 PMCID: PMC2875471 DOI: 10.1007/s00221-010-2254-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Accepted: 04/09/2010] [Indexed: 10/28/2022]
Abstract
Artificial sensations can be produced by direct brain stimulation of sensory areas through implanted microelectrodes, but the perceptual psychophysics of such artificial sensations are not well understood. Based on prior work in cortical stimulation, we hypothesized that perceived intensity of electrical stimulation may be explained by the population response of the neurons affected by the stimulus train. To explore this hypothesis, we modeled perceived intensity of a stimulation pulse train with a leaky neural integrator. We then conducted a series of two-alternative forced choice behavioral experiments in which we systematically tested the ability of rats to discriminate frequency, amplitude, and duration of electrical pulse trains delivered to the whisker barrel somatosensory cortex. We found that the model was able to predict the performance of the animals, supporting the notion that perceived intensity can be largely accounted for by spatiotemporal integration of the action potentials evoked by the stimulus train.
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Affiliation(s)
- Gene Y Fridman
- Biomedical Engineering Department, UCLA, Los Angeles, CA 90095, USA.
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Ni AM, Maunsell JHR. Microstimulation reveals limits in detecting different signals from a local cortical region. Curr Biol 2010; 20:824-8. [PMID: 20381351 DOI: 10.1016/j.cub.2010.02.065] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 02/04/2010] [Accepted: 02/23/2010] [Indexed: 12/01/2022]
Abstract
Behavioral performance depends on the activity of neurons in sensory cortex, but little is known about the brain's capacity to access specific neuronal signals to guide behavior. Even the individual sensory neurons that are most sensitive to a relevant stimulus are only weakly correlated with behavior, suggesting that behavioral decisions are based on the combined activity of groups of neurons with sensitivities well matched to task demands. To explore how flexibly different patterns of activity can be accessed from a given cortical region, we trained animals to detect electrical microstimulation of local V1 sites. By allowing the animals to become expert at the detection of microstimulation of specific V1 sites that corresponded to particular retinotopic locations, we could measure the effects of that training on the ability of those sites to support the detection of visual stimuli. Training to detect electrical activation caused a large, reversible, retinotopically localized impairment of thresholds for detecting visual stimuli. Retraining on visual detection restored normal thresholds and in turn impaired thresholds for detecting microstimulation. These results suggest that there are substantial limits to the types of signals for which a local cortical region can be simultaneously optimized.
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Affiliation(s)
- Amy M Ni
- Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
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40
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Masse NY, Cook EP. Behavioral Time Course of Microstimulation in Cortical Area MT. J Neurophysiol 2010; 103:334-45. [DOI: 10.1152/jn.91022.2008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Electrical stimulation of the brain is a valuable research tool and has shown therapeutic promise in the development of new sensory neural prosthetics. Despite its widespread use, we still do not fully understand how current passed through a microelectrode interacts with functioning neural circuits. Past behavioral studies have suggested that weak electrical stimulation (referred to as microstimulation) of sensory areas of cortex produces percepts that are similar to those generated by normal sensory stimuli. In contrast, electrophysiological studies using in vitro or anesthetized preparations have shown that neural activity produced by brief microstimulation is radically different and longer lasting than normal responses. To help reconcile these two aspects of microstimulation, we examined the temporal properties that microstimulation has on visual perception. We found that brief application of subthreshold microstimulation in the middle temporal (MT) area of visual cortex produced smaller and longer-lasting effects on motion perception compared with an equivalent visual stimulus. In agreement with past electrophysiological studies, a computer simulation reproduced our behavioral effects when the time course of a single microstimulation pulse was modeled with three components: an immediate fast strong excitatory component, followed by a weaker inhibitory component, and then followed by a long duration weak excitatory component. Overall, these results suggest the behavioral effects of microstimulation in our experiments were caused by the unique and long-lasting temporal effects microstimulation has on functioning cortical circuits.
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Affiliation(s)
- Nicolas Y. Masse
- Department of Physiology, McGill University, Montreal, Quebec, Canada
| | - Erik P. Cook
- Department of Physiology, McGill University, Montreal, Quebec, Canada
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41
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Dulay MF, Murphey DK, Sun P, David YB, Maunsell JHR, Beauchamp MS, Yoshor D. Computer-controlled electrical stimulation for quantitative mapping of human cortical function. J Neurosurg 2009; 110:1300-3. [PMID: 19061348 DOI: 10.3171/2008.2.jns17666] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Cortical mapping with electrical stimulation (ES) in neurosurgical patients typically involves the manually controlled delivery of suprathreshold electrical current to a discrete area of the brain. Limited numbers of trials and imprecise current delivery methods increase the variability of the behavioral response and make it difficult to collect quantitative mapping data, which is especially important in research studies of human cortical function. To overcome these limitations, the authors developed a method for computer-controlled delivery of defined electrical current to implanted intracranial electrodes. They demonstrate that stimulation can be time locked to a behavioral task to rapidly and systematically measure the detection threshold for ES in human visual cortex over many trials. Computer-controlled ES is well suited for the systematic and quantitative study of the function of virtually any region of cerebral cortex. It may be especially useful for studying human cortical regions that are not well characterized and for verifying the presence of stimulation-evoked percepts that are difficult to objectively confirm.
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Affiliation(s)
- Mario F Dulay
- Departments of Neurosurgery, Texas Children's Hospital, Houston Texas, USA
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Tehovnik EJ, Slocum WM. Background luminance affects the detection of microampere currents delivered to macaque striate cortex. Eur J Neurosci 2009; 30:263-71. [PMID: 19558620 DOI: 10.1111/j.1460-9568.2009.06810.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Monkeys detect electrical microstimulation delivered to the striate cortex (area V1). We examined whether the ability of monkeys to detect such stimulation is affected by background luminance. While remaining fixated on a spot of light centered on a monitor, a monkey was required to detect a 100 ms train of electrical stimulation delivered to a site within area V1 situated from 1 to 1.5 mm below the cortical surface. A monkey signaled the delivery of stimulation by depressing a lever after which it was rewarded with a drop of apple juice. Control trials were interleaved during which time no stimulation was delivered and the monkey was rewarded for not depressing the lever. Biphasic pulses were delivered at 200 Hz and the current ranged from 2 to 30 microA using 0.2 ms anode-first biphasic pulses. The background luminance level of the monitor could be varied from 0.005 to 148 cd/m(2). It was found that, for monitor luminance levels below 10 cd/m(2), the current threshold to evoke a detection response increased. We discuss the significance of this result with regard to phosphenes elicited from human V1 and in relation to visual perception.
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Affiliation(s)
- Edward J Tehovnik
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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43
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Abstract
Monkeys can detect electrical stimulation delivered to the striate cortex (area V1). We examined whether such stimulation is layer dependent. While remaining fixated on a spot of light, a rhesus monkey was required to detect a 100-ms train of electrical stimulation delivered to a site within area V1. A monkey signaled the delivery of stimulation by depressing a lever after which he was rewarded with a drop of apple juice. Control trials were interleaved during which time no stimulation was delivered and the monkey was rewarded for not depressing the lever. Biphasic pulses were delivered at 200 Hz, and the current was typically at or < 30 muA using 0.2-ms cathode-first biphasic pulses. For some experiments, the pulse duration was varied from 0.05 to 0.7 ms and anode-first pulses were used. The current threshold for detecting cathode-first pulses 50% of the time was the lowest (< 10 muA) when stimulation was delivered to the deepest layers of V1 (between 1.0 and 2.5 mm below the cortical surface). Also, the shortest chronaxies (< 0.2 ms) and the shortest latencies (< 200 ms) for detecting the stimulation were observed at these depths. Finally, anode-first pulses were most effective at evoking a detection response in superficial V1 and cathode-first pulses were most effective at evoking a detection response in deep V1 (> 1.75 mm below the cortical surface). Accordingly, the deepest layers of V1 are the most sensitive for the induction of a detection response to electrical stimulation in monkeys.
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Affiliation(s)
- Edward J Tehovnik
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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45
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Abstract
In this paper, placement parameters for microstimulation electrodes in a visual prosthesis are evaluated based on retinotopic models of macaque and human lateral geniculate nucleus. Phosphene patterns were simulated for idealized microwire electrodes as well as for currently available clinical electrodes. For idealized microwire electrodes, spacing as large as 600 microm in three dimensions would allow for over 250 phosphenes per visual hemifield in macaques, and over 800 in humans.
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Affiliation(s)
- John S Pezaris
- Neurosurgery Department, Massachusetts General Hospital, Boston, MA 02114, USA.
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46
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Tehovnik EJ, Slocum WM, Smirnakis SM, Tolias AS. Microstimulation of visual cortex to restore vision. PROGRESS IN BRAIN RESEARCH 2009; 175:347-75. [PMID: 19660667 DOI: 10.1016/s0079-6123(09)17524-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This review argues that one reason why a functional visuo-cortical prosthetic device has not been developed to restore even minimal vision to blind individuals is because there is no animal model to guide the design and development of such a device. Over the past 8 years we have been conducting electrical microstimulation experiments on alert behaving monkeys with the aim of better understanding how electrical stimulation of the striate cortex (area V1) affects oculo- and skeleto-motor behaviors. Based on this work and upon review of the literature, we arrive at several conclusions: (1) As with the development of the cochlear implant, the development of a visuo-cortical prosthesis can be accelerated by using animals to test the perceptual effects of microstimulating V1 in intact and blind monkeys. (2) Although a saccade-based paradigm is very convenient for studying the effectiveness of delivering stimulation to V1 to elicit saccadic eye movements, it is less ideal for probing the volitional state of monkeys, as they perceive electrically induced phosphenes. (3) Electrical stimulation of V1 can delay visually guided saccades generated to a punctate target positioned in the receptive field of the stimulated neurons. We call the region of visual space affected by the stimulation a delay field. The study of delay fields has proven to be an efficient way to study the size and shape of phosphenes generated by stimulation of macaque V1. (4) An alternative approach to ascertain what monkeys see during electrical stimulation of V1 is to have them signal the detection of current with a lever press. Monkeys can readily detect currents of 1-2 microA delivered to V1. In order to evoke featured phosphenes currents of under 5 microA will be necessary. (5) Partially lesioning the retinae of monkeys is superior to completely lesioning the retinae when determining how blindness affects phosphene induction. We finish by proposing a future experimental paradigm designed to determine what monkeys see when stimulation is delivered to V1, by assessing how electrical fields generated through multiple electrodes interact for the production of phosphenes, and by depicting a V1 circuit that could mediate electrically induced phosphenes.
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Affiliation(s)
- Edward J Tehovnik
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
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47
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Conditions that alter saccadic eye movement latencies and affect target choice to visual stimuli and to electrical stimulation of area V1 in the monkey. Vis Neurosci 2008; 25:661-73. [PMID: 19079822 DOI: 10.1017/s0952523808080863] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In this study, we examined procedures that alter saccadic latencies and target selection to visual stimuli and electrical stimulation of area V1 in the monkey. It has been shown that saccadic eye movement latencies to singly presented visual targets form a bimodal distribution when the fixation spot is turned off a number of milliseconds prior to the appearance of the target (the gap period); the first mode has been termed express saccades and the second regular saccades. When the termination of the fixation spot is coincident with the appearance of the target (0 ms gap), express saccades are rarely generated. We show here that a bimodal distribution of saccadic latencies can also be obtained when an array of visual stimuli is presented prior to the appearance of the visual target, provided the elements of the array overlap spatially with the visual target. The overall latency of the saccadic eye movements elicited by electrical stimulation of area V1 is significantly shortened both when a gap is introduced between the termination of the fixation spot and the stimulation and when an array is presented. However, under these conditions, the distribution of saccadic latencies is unimodal. When two visual targets are presented after the fixation spot, introducing a gap has no effect on which target is chosen. By contrast, when electrical stimulation is paired with a visual target, introducing a gap greatly increases the frequency with which the electrical stimulation site is chosen.
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48
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Striate cortical lesions affect deliberate decision and control of saccade: implication for blindsight. J Neurosci 2008; 28:10517-30. [PMID: 18923028 DOI: 10.1523/jneurosci.1973-08.2008] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Monkeys with unilateral lesions of the primary visual cortex (V1) can make saccades to visual stimuli in their contralateral ("affected") hemifield, but their sensitivity to luminance contrast is reduced. We examined whether the effects of V1 lesions were restricted to vision or included later stages of visual-oculomotor processing. Monkeys with unilateral V1 lesions were tested with a visually guided saccade task with stimuli in various spatial positions and of various luminance contrasts. Saccades to the stimuli in the affected hemifield were compared with those to the near-threshold stimuli in the normal hemifield so that the performances of localization were similar. Scatter in the end points of saccades to the affected hemifield was much larger than that of saccades to the near-threshold stimuli in the normal hemifield. Additional analysis revealed that this was because the initial directional error was not as sufficiently compensated as it was in the normal hemifield. The distribution of saccadic reaction times in the affected hemifield tended to be narrow. We modeled the distribution of saccadic reaction times by a modified diffusion model and obtained evidence that the decision threshold for initiation of saccades to the affected hemifield was lower than that for saccades to the normal hemifield. These results suggest that the geniculostriate pathway is crucial for on-line compensatory mechanisms of saccadic control and for decision processes. We propose that these results reflect deficits in deliberate control of visual-oculomotor processing after V1 lesions, which may parallel loss of visual awareness in human blindsight patients.
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Kawasaki K, Sheinberg DL. Learning to recognize visual objects with microstimulation in inferior temporal cortex. J Neurophysiol 2008; 100:197-211. [PMID: 18463185 DOI: 10.1152/jn.90247.2008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The malleability of object representations by experience is essential for adaptive behavior. It has been hypothesized that neurons in inferior temporal cortex (IT) in monkeys are pivotal in visual association learning, evidenced by experiments revealing changes in neural selectivity following visual learning, as well as by lesion studies, wherein functional inactivation of IT impairs learning. A critical question remaining to be answered is whether IT neuronal activity is sufficient for learning. To address this question directly, we conducted experiments combining visual classification learning with microstimulation in IT. We assessed the effects of IT microstimulation during learning in cases where the stimulation was exclusively informative, conditionally informative, and informative but not necessary for the classification task. The results show that localized microstimulation in IT can be used to establish visual classification learning, and the same stimulation applied during learning can predictably bias judgments on subsequent recognition. The effect of induced activity can be explained neither by direct stimulation-motor association nor by simple detection of cortical stimulation. We also found that the learning effects are specific to IT stimulation as they are not observed by microstimulation in an adjacent auditory area. Our results add the evidence that the differential activity in IT during visual association learning is sufficient for establishing new associations. The results suggest that experimentally manipulated activity patterns within IT can be effectively combined with ongoing visually induced activity during the formation of new associations.
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Affiliation(s)
- Keisuke Kawasaki
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912, USA
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50
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Bókkon I. Phosphene phenomenon: a new concept. Biosystems 2008; 92:168-74. [PMID: 18358594 DOI: 10.1016/j.biosystems.2008.02.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2007] [Revised: 02/10/2008] [Accepted: 02/12/2008] [Indexed: 02/01/2023]
Abstract
This paper proposes a new biopsychophysical concept of phosphene phenomenon. Namely, visual sensation of phosphenes is due to the intrinsic perception of ultraweak bioluminescent photon emission of cells in the visual system. In other words, phosphenes are bioluminescent biophotons in the visual system induced by various stimuli (mechanical, electrical, magnetic, ionizing radiation, etc.) as well as random bioluminescent biophotons firings of cells in the visual pathway. This biophoton emission can become conscious if induced or spontaneous biophoton emission of cells in the visual system exceeds a distinct threshold. Neuronal biophoton communication can occur by means of non-visual neuronal opsins and natural photosensitive biomolecules. Our interpretation is in direct connection with the functional roles of free radicals and excited biomolecules in living cells.
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Affiliation(s)
- István Bókkon
- PhD School in Pharmacology, Semmelweis University, Láng E. 68, H-1238 Budapest, Hungary.
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