P.H. Schiller, V.S. Weiner and E.J.
Tehovnik, 2005
Soc Neurosci. Abstr., 16.1.
Abstract
One of the important early steps in examining the feasibility of a visual prosthetic
device that electrically stimulates area V1 is to use an animal model. To do
so, we set out to determine what visual percepts are elicited with electrical
stimulation in rhesus monkeys. Here we examined the size and contrast of the
images produced. Monkeys were trained on two tasks. In the first, the paired
target task, either two visual stimuli were presented or one visual stimulus
was paired with electrical stimulation. The animal had a free choice in selecting
either stimulus with a saccadic eye movement. One of the visual targets appeared
within the receptive fields of the stimulated neurons. The visual targets were
circular. The relative size and contrast of the visual stimuli was varied. The
animals showed strong preference for the larger and higher contrast target.
Curves were generated that depicted their choice. The 50% crossover point represents
choice equivalence. In the second task, called the oddity discrimination task,
six stimuli were presented, one of which, the target, was different from the
other five, the distractors. The size and contrast of the distractors was varied
while the target was held constant. On selected trials the visual target was
replaced with electrical stimulation which in most cases was at 200Hz for 80ms,
ranging between 20 and 100A. The animals were tested at eccentricities of 2.5-3.5
from the fovea. We established that the size of the percept for the monkey for
both procedures ranged between 14-18 minutes of visual angle in diameter with
a contrast of 6 to 12%. Increasing the current from 20 to 80A increased the
perceived contrast of the phosphene up to 12% contrast. The size of the phosphene
was not significantly altered with increasing current. The phosphene was approximately
the size of the average receptive field of the stimulated neurons. These findings
suggest that the percepts elicited in monkeys by electrical stimulation are
similar to those reported in man.
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Citation: P.H. Schiller, V.S. Weiner, E.J. Tehovnik. PRELIMINARY STUDIES EXAMINING THE FEASIBILITY OF A VISUAL PROSTHETIC DEVICE: 1. WHAT DOES A MONKEY SEE WHEN AREA V1 IS STIMULATED ELECTRICALLY? Program No. 16.1. 2005 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2005. Online.