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Title: Spatial Restriction of Neural Activation Using Focused Multipolar Stimulation With a Retinal Prosthesis
Authors: Spencer, Thomas
Fallon, James
Thien, Patrick
Shivdasani, Mohit
Keywords: Retinal prosthesis
Electrical stimulation
Current focusing
In vivo physiology
Suprachoroidal
Issue Date: Jun-2016
Publisher: IOVS
Citation: Spencer, T. C., J. B. Fallon, P. C. Thien, and M. N. Shivdasani. 2016. Spatial Restriction of Neural Activation Using Focused Multipolar Stimulation With a Retinal Prosthesis. Investigative Ophthalmology & Visual Science. 57: 3181-91.
Abstract: PURPOSE: The resolution provided by present state-of-the-art retinal prostheses is severely limiting for recipients, partly due to the broad spread of activation in the retina in response to monopolar (MP) electrical stimulation. Focused multipolar (FMP) stimulation has been shown to restrict neural activation in the cochlea compared to MP stimulation. We extended the FMP stimulation technique to a two-dimensional electrode array and compared its efficacy to MP and hexapolar (HP) stimulation in the retina. METHODS: Normally-sighted cats (n = 6) were implanted with a suprachoroidal electrode array containing 42 electrodes. Multichannel multiunit spiking activity was recorded from the visual cortex in response to MP, HP, and FMP retinal stimulation. RESULTS: When inferring retinal spread using voltage recordings off the stimulating array, FMP stimulation showed significantly reduced voltages in regions surrounding the primary stimulating electrode. When measuring the retinal and cortical selectivity of neural responses, FMP and HP stimulation showed significantly higher selectivity compared to MP stimulation (separate 2-way ANOVAs, P < 0.05). However, the lowest cortical thresholds for each stimulating electrode were higher for FMP and HP compared to MP stimulation (1-way ANOVA, P < 0.001). No significant differences were observed between FMP and HP stimulation in any measures. CONCLUSIONS: Focused multipolar and HP stimulation using a two-dimensional array are promising techniques to reduce the spread of activation for a retinal prosthesis. Clinical application would be expected to result in smaller phosphenes; thus, reducing phosphene overlap between electrodes and increasing the resolution at the expense of higher thresholds for activation.
URI: http://repository.bionicsinstitute.org:8080/handle/123456789/237
ISSN: 1552-5783 (Electronic) 0146-0404 (Linking)
Appears in Collections:Bionic Vision Research Publications

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