Rapid functional plasticity of the somatosensory cortex after finger amputation

Recent research indicates that areas of the primary somatosensory (SI) and primary motor cortex show massive cortical reorganization after amputation of the upper arm, forearm or fingers. Most of these studies were carried ou t months or several years after amputation. In the present study, we descri be cortical reorganization of areas in the SI of a patient who underwent am putation of the traumatized middle and ring fingers of his right hand 10 da ys before cortical magnetic source imaging data were obtained. Somatosensor y-evoked;ed magnetic fields (SEF) to mechanical stimuli to the finger tips were recorded and single moving dipoles were calculated using a realistic v olume conductor model. Results reveal that the dipoles representing the sec ond and fifth fingers of the affected hand were closer together than the co mparable dipoles of the unaffected hand. Our findings demonstrate that neur al cell assemblies in SI which formerly represented the right middle and ri ng fingers of this amputee became reorganized and invaded by neighbouring c ell assemblies of the index and little finger of the same hand. These resul ts indicate that functional plasticity occurs within a period of 10 days af ter amputation.