Sustained Functional Plasticity can be Induced in Human Parietal Cortex with Adaptation to Reversed Visual Input

As an avenue to explore the extent to which human posterior parietal cortex (PPC) can undergo dynamic reorganization, we used fMRI to investigate the cortical effects of an extreme alteration of visual input. In Experiment-1, subjects adapted to a complete left-right visual-field reversal for two weeks continuously. After 7-10 days, subjects adapted behaviorally, and, in tandem, visual fields in their PPC shifted their visuospatial representations from primarily contralateral to ipsilateral visual field responses. When normal vision was restored, subjects’ behavior and PPC visual-field-map spatial representations returned to normal within one day, indicating that the original contralateral representations were maintained. In Experiment-2, we tested whether these ipsilateral representations persisted by returning the same subjects to the reversed visual environment and showed behavioral and cortical PPC adaptation now occurred within one day. Our results indicate that our subjects’ behavioral adaptation was subserved in PPC visual field maps by functional plasticity: persistent, experience-dependent changes in cortical representations. Understanding such induction of functional plasticity in cortex grants insight into the nature of these visuomotor systems and may foster the development of therapies for cortical damage.