Title

Directional bias of neurons in V1 and V2 of strabismic monkeys: temporal-to-nasal asymmetry?

Authors

Ichiro Watanabe, University of Houston
Hua Bi, Nova Southeastern UniversityFollow
Bin Zhang, University of HoustonFollow
Eiichi Sakai, University of Houston
Takafumi Mori, University of Houston
Ronald S. Harwerth, University of Houston
Earl L. Smith III, University of HoustonFollow
Yuzo M. Chino, University of HoustonFollow

ISBN or ISSN

0146-0404

Volume

46

Issue

10

Publication Date / Copyright Date

10-1-2005

First Page

3899

Last Page

3905

DOI Number

10.1167/iovs.05-0563

Abstract

PURPOSE:

Strabismus that develops shortly after birth is known to cause temporal-to-nasal eye movement asymmetries under monocular viewing. The neural mechanisms underlying this deficit are not well understood. In the current study, the hypothesis that this eye movement anomaly reflects a similar asymmetry in the directional response properties of neurons in the early stages of cortical processing was examined.

METHODS:

Strabismus was simulated with optical methods in infant monkeys between 4 and 14 weeks of age. When the monkeys were mature, microelectrode recording experiments were conducted in the primary visual cortex (V1) and visual area 2 (V2). After the spatial frequency of sine wave-grating stimuli for each neuron was optimized, each neuron's responsiveness to 24 directions of stimulus movement was measured. The preferred direction and the strength of directional bias were determined by a vector summation method.

RESULTS:

There was not an overabundance of neurons in V1 or V2 of strabismic monkeys preferring the temporal-to-nasal direction of stimulus movement. However, the average directional bias was significantly reduced in these strabismic monkeys. Interocular suppression was highly prevalent, and this suppression was stronger and more common in neurons dominated by the ipsilateral eye.

CONCLUSIONS:

The results suggest that the eye movement asymmetries in strabismic subjects do not result from similar asymmetries in the directional properties of V1 or V2 neurons, but rather reflect impoverished cortical signals to the brain stem nuclei that control eye movements.

Disciplines

Optometry

NSUWorks Citation

Watanabe, Ichiro; Bi, Hua; Zhang, Bin; Sakai, Eiichi; Mori, Takafumi; Harwerth, Ronald S.; Smith, Earl L. III; and Chino, Yuzo M., "Directional bias of neurons in V1 and V2 of strabismic monkeys: temporal-to-nasal asymmetry?" (2005). Faculty Articles. 9.
https://nsuworks.nova.edu/hpd_opt_facarticles/9