NSUCO - The Visionary Spring 2012

THE V ISIONARY • S PRING 2012 — 20 Ocular dominance distribution of V1 (top) and V2 neurons (bottom) for normal monkeys, monkeys with mild amblyopia (AI < 0.5), and monkeys with severe amblyopia (AI > 0.5). AI, amblyopic index. ROII, relative ocular dominance imbalance. A, amblyopic eye; NA, fellow “nonamblyopic” eye; R, right eye; L, left eye. Open histograms show the prevalence of “binocularly balanced cells” and filled histograms show binocularly imbalanced/monocular cells. Dr. Bi continued... THE DEVELOPMENT OF THE RECEPTIVE FIELD INTERNAL STRUCTURE OF V2 NEURONS IN PRIMATES Bin Zhang, M.D., Ph.D. Associate Professor of Optometry Ocular dominance distribution of V1 (top) and V2 neurons (bottom) for normal monkeys, monkeys with mild amblyopia (AI < 0.5), and monkeys with severe amblyopia (AI > 0.5). AI, amblyopic index. ROII, relative ocular dominance imbalance. A, amblyopic eye; NA, fellow “nonamblyopic” eye; R, right eye; L, left eye. Open histograms show the prevalence of “binocularly balanced cells” and filled histograms show binocularly imbalanced/monocular cells. Providing brief daily periods of unrestricted vision during early monocular form deprivation reduces the depth of amblyopia. To study the neural basis of this treatment, Dr. Zhang quantitatively an- alyzed the binocular and monocular response properties of neurons in visual area 2 (V2) of form-deprived macaque monkeys. Dr. Zhang found that the ocular dominance imbalance away from the affected eye was reduced in the experimental monkeys and was generally proportional to the reduction in the depth of amblyopia in individual monkeys. There were no interocular differences in the spatial prop- erties of V2 neurons in any subject group. However, the binocular disparity sensitivity of V2 neurons was sig- nificantly higher and binocular suppression was lower in monkeys that had unrestricted vision. These findings showed that the de- crease in ocular dominance imbalance in V2 was the neuronal change most closely associated with the observed reduction in the depth of amblyopia. The results suggest that the degree to which extrastriate neurons can maintain functional connections with the deprived eye (i.e., reducing undersampling for the affected eye) is the most significant factor associated with the beneficial effects of brief periods of unrestricted vision. Final section of cover story continued on next page with Dr. Wagner...