Short-term monocular deprivation enhances 7T BOLD responses and reduces neural selectivity in V1

Abstract

Recent studies have shown that short-term (2h) monocular deprivation unexpectedly increases the dominance of the deprived eye in binocular rivalry, and induces a decrease of GABA concentration in the visual cortex of adult humans. GABAergic inhibition is key to determining the selectivity of neural responses, through intra-cortical lateral inhibition. A decrease of GABA after monocular deprivation would predict an increase of BOLD responses and a reduction of neuronal selectivity. We measured BOLD (at 7T) selectivity to ocular dominance and to spatial frequency by presenting narrow band-pass visual noise monocularly before and after deprivation in 10 young human adults. Using a population Receptive Field mapping approach, we modeled the responses to 5 stimuli that had the same bandwidth of 1.5oct and preferred spatial frequencies of 0.15, 0.25, 0.5, 1.3 and 3cpd to estimate the spatial frequency tuning of early visual cortex voxels. In order to assess the effect of deprivation, we also measured eye-dominance with binocular rivalry before and after deprivation and immediately before scanning. We found that monocular deprivation boosted BOLD responses in early visual areas. In V1 the boost was stronger for the deprived eye and for higher spatial frequencies, indicating a change of neural tuning for both eye-dominance and spatial frequency. At the population level, the scatter of responses increased after deprivation and the spatial frequency selectivity became broader. Importantly, the selectivity of the V1 post-deprivation BOLD responses for the deprived eye correlated with the psychophysical index of visual plasticity: observers with a stronger boost of the deprived eye in binocular rivalry had a broader tuning for eye-dominance and spatial frequency. This enhanced integration is consistent with the reduction of GABAergic inhibition of lateral inhibition and may reflect the optimal response to the homeostatic gain change that is transiently produced by the reduced stimulation of the deprived eye.

Meeting abstract presented at VSS 2017