Blindness produces yoked changes in V1 cortical thickness, cross-modal responses, and resting metabolism.
35.11, Sunday, May 12, 5:15 - 7:00 pm, Royal Ballroom 1-3
Ritobrato Datta1, Aleksandra B. Daina1, Lauren Brandes1, Efstathios D. Gennatas2, Sashank Prasad1, Omar H. Butt1, Geoffrey K. Aguirre1; 1Department of Neurology, University of Pennsylvania, Philadelphia 19104, 2Department of Psychiatry, University of Pennsylvania, Philadelphia 19104
Blindness alters brain structure and function, but whether these specific changes are related or independent across subjects has not been examined. We tested the hypothesis that blind individuals with thickened striate cortex (indicative of altered synaptic pruning) would show linked changes in cross-modal neural response and resting blood flow. 37 blind (55±12 years) and 23 sighted (38±17) participants were studied. fMRI data were collected at rest in darkness and during a semantic decision task (plausibility judgement of spoken sentences). MPRAGE, resting perfusion and DTI were also acquired. Mean cerebral blood flow (CBF), cross-modal activation to auditory sentences (BOLD %), cortical thickness, and surface area were measured within V1. Functional connectivity between V1 and somatosensory and BrocaÂ’s area were calculated from rest data. Volumes and fractional anisotropy (FA) of the optic and radiations, pericalcarine white matter, and splenium were obtained. We replicated prior work, finding significant differences between the sighted and blind groups in almost every measure. We then examined if there exist correlations across blind subjects in structural and functional alterations which may not be present in the sighted group. Cortical thickness was significantly correlated (and V1 surface area negatively correlated) with cross-modal activation (r=0.51), which in turn was strongly correlated with V1 perfusion at rest (r=0.47) and long-range functional connectivity with somatosensory cortex (r=0.63). Interestingly, anatomical measures of the anterior visual pathway (chiasmal volume and FA, optic radiation FA) were not correlated with these alterations. Our results provide a direct link between presumed alterations in cortical maturation in blindness that lead in turn to preserved long-range functional connections, and cross-modal representation. Further, these "compensatory" changes appear to be independent from the "degeneration" changes in the anterior visual pathway associated with damage to the neural retina.