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Spatial Restriction of Neural Activation Using Focused Multipolar Stimulation With a Retinal Prosthesis
Thomas C Spencer1, James B Fallon1, Patrick C Thien1
1Bionics Institute, East Melbourne, Australia 2Department of Medical Bionics, The University of Melbourne, East Melbourne, Australia.
Investigative Ophthalmology & Visual Science
|June 17, 2016
Summary
Focused multipolar (FMP) and hexapolar (HP) retinal stimulation reduced neural activation spread compared to monopolar (MP) stimulation. While FMP and HP offer higher selectivity for retinal prostheses, they require higher activation thresholds.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Ophthalmology
Background:
- Current retinal prostheses have limited resolution due to broad neural activation from electrical stimulation.
- Monopolar (MP) stimulation causes widespread retinal activation, hindering visual prosthesis efficacy.
- Focused multipolar (FMP) stimulation has shown promise in reducing neural activation spread in auditory prostheses.
Purpose of the Study:
- To evaluate the efficacy of FMP stimulation compared to MP and hexapolar (HP) stimulation in the retina.
- To assess the potential of FMP stimulation to improve the resolution of retinal prostheses.
Main Methods:
- A 42-electrode suprachoroidal array was implanted in normally-sighted cats (n=6).
- Multichannel multiunit spiking activity was recorded from the visual cortex.
- Electrical stimulation was delivered using MP, HP, and FMP configurations.
Main Results:
- FMP stimulation demonstrated significantly reduced voltage spread around the stimulating electrode compared to MP.
- Both FMP and HP stimulation showed significantly higher retinal and cortical selectivity than MP stimulation (P < 0.05).
- FMP and HP stimulation exhibited higher cortical activation thresholds than MP stimulation (P < 0.001).
Conclusions:
- FMP and HP stimulation, using a 2D array, effectively reduce neural activation spread in the retina.
- These techniques hold promise for improving retinal prosthesis resolution by minimizing phosphene overlap.
- Clinical implementation may involve a trade-off between increased resolution and higher activation thresholds.
