College of Optometry Faculty Proceedings, Presentations, Posters, Speeches, Lectures, etc.

Title

Interocular Cross-Orientation Suppression In V1 Neurons Of Strabismic Monkeys

Format

Poster

Conference Title

Society of Neuroscience Annual Meeting

Organization/Association/Group

Society of Neuroscience

Location

Orlando, Florida / November 3-7, 2002

Publication Date / Copyright Date

11-6-2002

Abstract

Monkeys reared with strabismus show a higher than normal prevalence of V1 neurons that exhibit interocular suppression. The purpose of this study was to investigate a source of this suppression. Strabismus was optically simulated in 4 infant rhesus monkeys using a prism-rearing procedure. The onset of strabismus was at 2 or 6 weeks of age and the duration was only for 14 days. Four age-matched normal monkeys served as controls. Immediately after the rearing regimen, we conducted the recording experiments in order to compare the responses of V1 units to binocularly matched (iso-oriented) pairs of sine-wave gratings with their responses to orthogonally oriented, dichoptic gratings. We found that in strabismic infants, the prevalence of interocular suppression for the orthogonally oriented gratings was nearly identical to that for binocularly matched gratings. In normal infants, suppressive units were more prevalent for orthogonally oriented stimuli. With respect to the strength of suppression, about one half of the neurons in our strabismic monkeys showed binocular over monocular response ratios that were similar for the two stimulus conditions. The remaining units showed substantial differences in this ratio favoring one stimulus condition over the other. These results support the hypothesis that interocular suppression is the predominant binocular interaction in strabismic monkeys and that abnormal suppressive interactions occur because conflicting binocular inputs early in life reduce the effectiveness of excitatory binocular connections, both local and long-range, while largely sparing, at least relatively, inhibitory connections.

Disciplines

Optometry

Keywords

striate cortex, strabismus, early development, electrophysiology

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