We examined the effects of electrical stimulation of area V1 in the monkey to determine the feasibility of using implanted electrode arrays as a visual prosthesis. Area V1 in the monkey is lissencephalic making for easy access; the visual field is laid out topographically and the receptive fields of the neurons are quite small. Our experiments show the following: 1. Low levels of electrical stimulation reveal laminar specificity; when electrical stimulation is paired with a visual target presented in the receptive field of the stimulated neurons, in the upper layers target selection is interfered with whereas in the lower layers target selection is facilitated. 2. Systematic variation of the placement of the visual stimulus relative to the receptive field of the electrically stimulated neurons reveals that the interference produced is local and affects only a small circular area approximately the size of the receptive field of the stimulated neurons. 3. Examining the nature of the visual percept created with electrical stimulation shows that stimulation for 80 milliseconds at 200 Hz between 20 and 120 microamps applied to neurons with receptive fields at 2.5–3.5 degrees of eccentricity produces an image that has a contrast of 6–12 percent and a size of 14–18 minutes of visual angle in diameter.
We believe that the use of implanted electrode arrays has the potential of providing visual information for the blind. We infer, furthermore, that successive activation of electrodes will be able to provide motion information including motion parallax for depth perception.
Supported by NEI NIH EY014884