Abstract
Cortical reorganization after lesions to primary somatosensory cortex (S1) has been studied extensively in animal models, yet little is known regarding post-stroke sensorimotor plasticity in humans. We examined two brain-damaged individuals, LS and RF, who suffered lesions in the hand area of right S1 and posterior parietal cortex with spared motor cortex. Behavioral investigations revealed expected deficits in tactile detection and tactile localization in the contralesional limb in both patients, while the ability to perform simple hand movements was preserved. We then conducted functional neuroimaging experiments in which they received tactile stimulation or performed hand movements (opening-closing the fist). For LS, whose damage encompassed the entire hand area of S1, tactile stimulation on the contralesional right hand activated secondary somatosensory area (S2) and middle temporal gyrus. RF’s lesion was slightly different with a spared strip of S1 along the posterior bank of the central sulcus. When presented with tactile stimuli, she demonstrated activation in spared S1. When moving the contralesional hand, RF showed bilateral activity in sensorimotor cortex, whereas LS showed stronger activation in bilateral putamen and deactivation in ipsilateral cerebellum, indicating reweighting in the motor system. Surprisingly, when moving the contralesional hand, both patients showed significantly greater activation in lateral occipital cortex compared to eight age-matched controls. These results suggest the recruitment of body representations in visual areas after damage to somatosensory cortex, either due to increased visual imagery of the limbs due to reduced sensory feedback or some form of post-stroke plasticity and/or reweighting.