Finger representations in human primary somatosensory cortex as revealed by high-resolution functional MRI of tactile stimulation

Fine-scale functional organization of the finger areas in the human primary somatosensory cortex was investigated by high-resolution BOLD MRI at 3 T using a multi-echo FLASH sequence with a voxel size of 2 mm3. In six subjects independent tactile stimulation of the distal phalanx of the fingers of the right hand resulted in small circumscribed and barely overlapping activations precisely located along the posterior wall of the central sulcus. Three out of six subjects showed a complete succession of activation sites for all five fingers. The maps also allowed for the identification of individual variations in finger somatotopy. When registered onto the individual high-resolution MRI anatomy and compared with cytoarchitectonical maps, the finger representations were confirmed to lie within Brodmann area 3b as the main input region of the primary somatosensory cortex.