Short-term Monocular Deprivation changes Thalamo-Cortical Connectivity measured with ultra-high field fMRI during visual stimulation

In adult humans, brief periods of monocular deprivation induce ocular dominance plasticity, transiently enhancing responses to stimuli in the deprived eye in the primary visual cortex V1 (Binda et al., 2018) and the ventral pulvinar (Kurzawski et al., 2022). Prior work (Acquafredda et al., VSS2023) suggests that these changes are accompanied by a functional reorganization of visual processing circuits, particularly cortico-pulvino-cortical loops, measured in resting-state. Here we investigated how thalamo-cortical connectivity is modulated by visual stimulation of either eye, before and after deprivation. We acquired ultra-high-field 7T fMRI EPI sequences from 22 normally sighted adults, pre- and post-2 hours of monocular deprivation. Participants were presented with monocular band-pass noise stimuli with five contrast levels. BOLD responses were analyzed for three regions of interest: V1, lateral geniculate nucleus, and pulvinar. Their effective connectivity was assessed by Dynamic Causal Modeling (Tapas toolbox, Frassle et al., 2017). Post-deprivation, V1 evoked responses increased for the deprived eye and decreased for the non-deprived eye, and the modulation was stronger for higher contrast stimuli, consistent with a response gain change. During deprived eye stimulation, pulvinar-to-V1 effective connectivity decreased post-deprivation (like in the resting state) while the V1-pulvinar connectivity remained constant. During stimulation of the non-deprived eye, the opposite connectivity changes were observed. These results suggest that monocular deprivation produces a disconnection between pulvinar and V1, probably decreasing V1 top-down modulation. The mirror-symmetric effect for the non-deprived eye recapitulates the symmetric modulation observed psychophysically. Overall, resting state and visual-evoked results suggest that brief periods of monocular deprivation produce changes in visual processing that extend beyond local V1 processes and may reflect a reorganization of top-down visual influence in V1.