Abstract
Understanding the extent and nature of cortical plasticity in human vision remains a key challenge for neuroscience. Given the bilateral cortical organization of both early and higher-order visual cortex, the visual system post-hemispherectomy/lobectomy offers a unique opportunity to explore cortical reorganization. Here, we report a longitudinal case study of a young male patient who underwent surgical removal of the entire right occipital and posterior temporal lobe at age 6.9 years. In order to 1) examine how extensive removal of the right ventral visual pathway alters the dynamics of the visual processing in the remaining cortex, and 2) characterize reorganization in category-selective regions over time, we used the same fMRI scanning protocol three times at 6 month intervals (starting 1 year post-surgery) to map category-selective activations (face, scene, object, and word). Whereas selectivity for scenes and objects remained stable across all three sessions, changes were most evident in the face- and word-selective regions. Although the developing face network largely involved a remapping to the left hemisphere (which is not typically specialized for face processing), it is consistent with evidence from the behavioral investigation that revealed age-appropriate face recognition abilities in this child. A substantial increase in word-selective activation was also observed in the left hemisphere with a significant lateral shift in both the peak and centroid of activation over time, suggesting competition between face- and word-processing when both are confined to a single hemisphere. Last, but not least, these dynamic changes in higher-order visual cortex occurred despite the limited plasticity in the earlier parts of visual cortex, as reflected by retinotopic mapping and behavioral visual perimetry testing. Overall, these findings reveal that, following extensive removal of visual cortex, there is limited plasticity in early visual cortex but developing and reorganized selectivity for several visual categories, accompanied by good visual performance.
Meeting abstract presented at VSS 2016