Neural plasticity in the somatosensory system

The mammalian brain is capable of a substantial functional reorganization, manifesting on a cortical somatotopical and on a behavioral level. Possible mechanisms are reviewed based on the work by others and ourselves on somat osensory reorganization in humans. The somatosensory system is characterize d by divergent projections from the periphery to the cerebral cortex. Chang es in synaptic weights allow for reorganization of sensory processing: On o ne side, limb amputation will result in a representational "invasion" of th e deafferentated cortex from neighboring regions with concomitant perceptua l changes. On the other side, sensorimotor training can increase the repres entational cortical zone of a limb. Plastic changes can be temporary or per sistent. Modulating factors like pain and certain drugs seem to induce a pe rmissive state in the cortex resulting in enhanced reorganization. Thus, sp ecific physical training combined with pharmacoceutical modulation holds pr omise to improve functional recovery after brain lesions.