Spatial attention modulates the cortical somatosensory representation of the digits in humans

THE topographic organization of the primary somatosensory cortex adapts to alterations of efferent input. Here, electric source imaging was used to sh ow that spatial attention modifies cortical somatosensory representations i n humans. The cortical representation of the electrically stimulated digit 2 (resp. digits 2 and 3) of the right hand was more medial along the somato sensory area 3b in subjects who focused attention on digit 4 of the right h and, while it was more lateral when subjects attended digit 4 of the contra lateral hand. This effect was very fast since the direction of attention wa s changed every 6 min, The results indicate that cortical somatosensory rep resentations not only depend on afferent input but vary when spatial attent ion is directed towards different parts of the body. (C) 1999 Lippincott Wi lliams & Wilkins.