Short-term ocular dominance changes in human V1.

Abstract

Ocular dominance describes the contribution of each eye to binocular vision. This balance is disrupted in some clinical conditions such as amblyopia. It has been shown psychophysically that short-term monocular deprivation shifts the equilibrium towards the occluded eye (1). In this study, we wanted to investigate the cortical mechanism underlying this phenomenon using magnetoencephalography (MEG). Subjects were presented with monocular and dichoptic stimuli using a frequency tagging paradigm to identify the input coming from each eye. Three 10-minute blocks of MEG recordings were followed by 2.5 hours of monocular deprivation. Immediately after removal of the patch, another three consecutive blocks were recorded followed by a final recording 45 min post deprivation. Immediately following the removal of the patch, we observed an increase in power of the response from the occluded eye as early as in V1, and reflected in the response of subsequent brain areas as well. At the same time, the power of the response from the undeprived eye was reduced. The pre-deprivation ocular power distribution was achieved again at the 45 min post-deprivation recording. The power redistribution was observed both monocularly and dichoptically, but was more pronounced on dichoptic recording. We also observed an increase in variability of the response from the occluded eye post-deprivation. In conclusion, short-term monocular deprivation perturbes the binocular equilibrium as measured psychophysically. We were able to observe a physiological correlate of this perturbation in area V1 of the visual cortex with MEG. The change in V1 neuronal population activity observed here might be a direct consequence of the underlying plasticity occurring in the brain.

Meeting abstract presented at VSS 2015