Reorganization of the hand somatosensory cortex following perinatal unilateral brain injury

Functional magnetic resonance imaging was used to map the hand somatosensor y cortices of nine hemiparetic young adult patients with perinatal unilater al brain injury in the sensorimotor area and five normal subjects. Stimulat ion of the paretic hand by periodic manual squeezing produced activation in the contralateral hemisphere of three patients and in the ipsilateral hemi sphere of three other patients. Paretic hand stimulation produced no activa tion in either hemisphere of the remaining three patients. Therefore, one-t hird of the patients demonstrated functional "plasticity" of the brain in t he form of inter-hemispheric relocation of the hand somatosensory function. The volume and pattern of activation for both hands was altered for those patients that showed evidence of cortical reorganization to the opposite he misphere. This differs from the hand motor system, which exhibited inter-he mispheric reorganization in a higher proportion of a related group of hemip aretic subjects.