Functional anatomy of the therapeutic effects of prism adaptation on left neglect

To investigate the anatomic substrates underlying the beneficial effect of prism adaptation in five patients with persistent left neglect following right stroke. In a functional imaging PET study, we used a covariation analysis to examine linear changes of regional cerebral blood flow over sessions as a function of left neglect improvement. The network of significant brain regions associated with improvement of left neglect performance produced by prism adaptation involved the right cerebellum, the left thalamus, the left temporo-occipital cortex, the left medial temporal cortex, and the right posterior parietal cortex. Our results suggest that the realignment of visuomotor coordinates is processed by the cerebellum and that low level sensorimotor adaptation actively modulates cerebral areas, albeit now relying on intact cerebellocerebral connections. Hence, our data support the hypothesis that the beneficial effect of prism adaptation on the clinical presentation of left neglect derives from modulation of cortical regions implicated in spatial cognition.