fMRI shows multiple somatotopic digit representations in human primary somatosensoy cortex

Using electrical finger nerve stimulation in normal human subjects, fMRI de tected separate representations for all 5 fingers in the primary somatosens ory cortex. Responses were located in the posterior wall of the deep centra l sulcus (most likely corresponding to Brodmann Area (BA) 3b), and the ante rior (BA 1) or posterior crown of the postcentral gyrus (BA 2) with rare ac tivations in BA 3a and 4. In BA 3b we found a regular somatotopic mediolate ral digit arrangement for fingers 5 to 1 with a mean Euclidean distance of 16 mm between fingers 1 and 5. In contrast BA 1/2 showed a greater number o f adjacent activation foci with significantly more overlap and partly even reversed ordering of neighbouring fingers. NeuroReport 11:1487-1491 (C) 200 0 Lippincott Williams & Wilkins.