Matthew C. Macdonald-Dale¹, Stefania S. Moro^1,2, Diana J. Gorbet¹, Remy Cohan¹, Peter J. Kohler¹, Jennifer K. E. Steeves^1,2; ¹Centre for Vision Research, York University, Toronto, Canada, ²The Hospital for Sick Children, Toronto, Canada

The surgical removal of one eye (monocular enucleation) early in life results in partial visual deprivation and offers a unique model for examining the consequences of the loss of binocularity on the maturation of the visual system. Adults who have undergone early monocular enucleation exhibit several long-term visual, auditory, and audiovisual behavioural adaptations as well as structural and functional adaptations within and between cortical and subcortical regions. In the current study, we investigated whether topographically organized visual cortex is influenced by the reduction in input to the visual system following monocular enucleation. We used functional Magnetic Resonance Imaging (fMRI) to map population Receptive Fields (pRFs) in individuals who have had one eye removed, as well as binocularly intact controls. pRF mapping was performed using a standard checkerboard bar swept across the visual field while participants performed a central fixation task. For each location on the cortical surface, we determined the size and visual field location of the pRF that accounted for the maximum variance in the observed fMRI signal. In early visual areas (V1, V2, and V3) of both hemispheres, pRFs were systematically larger for people with one eye compared to controls. Additionally, there was a larger rate of pRF expansion with eccentricity in the hemisphere contralateral to the remaining eye. No differences were observed for other parameters, including overall model fit, eccentricity, or gain. In summary, monocular enucleation may induce sensory plasticity where neurons in early visual cortex respond to a larger portion of the visual world. This is consistent with previous reports of reorganization within the LGN contralateral to the remaining eye and increased surface area in the primary visual cortex following monocular enucleation. These findings, in conjunction with behavioural and neuroimaging studies, contribute to the broader understanding of the effects of sensory deprivation from eye enucleation.

Acknowledgements: This research was supported by grants from Canada First Research Excellence Fund: Vision Science to Application (VISTA) (CFREF-2015-00013); Natural Sciences and Engineering Research Council of Canada (NSERC) (327588); Canada Foundation for Innovation (CFI) (12807).