Summary Lobectomy (resection of a portion of a cortex) or hemispherectomy (removal of a hemisphere) is an increasingly common treatment for seizure management in individuals with pharmaco-resistant epilepsy. Despite the removal of a considerable amount of visual cortex, these patients typically exhibit a remarkable degree of recovery of visuo-cognitive function, particularly if the resection is performed in early childhood. This restitution of function is all the more surprising given the distinct patterns of lateralization of the two cerebral hemispheres in the normal brain. The proposed research undertakes a systematic examination of the extent and nature of the recovery of visual abilities following cortical resection in children. Comparisons to matched typical controls and to children with non-visual cortex resection are made both at the group- level and for each individual, an important focus given the heterogeneity of this rare population. Cutting- edge psychophysical and neuroimaging procedures, and novel analytic approaches, elucidate the nature and changes in the cortical visual system pre- and post-surgery, and longitudinally thereafter, as well as the mechanisms that give rise to recovery, potential modulatory effects of brain regions outside the visual system, and possible biographical factors predicting recovery (e.g., age, side and size of resection). A first aim is to characterize the time-course of recovery in patients longitudinally and in detail, by collecting neural and behavioral data pre-surgery and 6, 12, and 18 months post-surgery, characterizing the changes in cortical selectivity, spatial topography, morphometric structure and behavioral competence in the patients. A second aim examines with precision the integrity of the brain and behavior, assessing fine- grained neural representations and a set of well-established computational properties exhibited by the normal visual system. A final aim involves acquiring whole brain data driven in response to a naturalistic movie viewing paradigm, to evaluate changes outside of the visual system that might influence and interact with the observed recovery at the group and individual levels. Alternative theoretical accounts for recovery of function are evaluated throughout. Little systematic research has targeted the patterns of visual deficits and their recovery following surgical resection in children, and even less attention has been devoted to determining the underlying factors that support (or potentially enhance) this plasticity. The study of an under-explored pediatric patient population, and the use of detailed behavioral and neuroimaging data acquisition, breaks new ground in both the basic and translational science of the visual system. Tracking these changes longitudinally with fine-grained methods provides unprecedented insights into the nature of plasticity in the visual system, and may, ultimately, inform the design of clinical interventions that facilitate functional...