The sensory somatotopic map of the human hand demonstrated at 4 Tesla

Recent attempts at high-resolution sensory-stimulated fMRI performed at 1.5 T have had very limited success at demonstrating a somatotopic organizatio n for individual digits. Our purpose was to determine if functional MRI at 4 T can demonstrate the sensory somatotopic map of the human hand. Sensory functional MRI was performed at 4 T in five normal volunteers using a low-f requency vibratory stimulus on the pad of each finger of the left hand. A s imple motor control task, was also performed. The data were normalized to a standard atlas, and individual and group statistical parametric maps (SPMs ) were computed for each task. Volume of activation and distribution of clu ster maxima were compared for each task. For three of the subjects, the SPM s demonstrated a somatotopic organization of the sensory cortex. The group SPMs demonstrated a clear somatotopic organization of the sensory cortex. T he thumb to fifth finger were organized, in general, with a lateral to medi al, inferior to superior, and anterior to posterior relationship. There was overlap in the individual SPMs between fingers. The sensory activation spa nned a space of 12-18 mm (thumb to fifth finger) on the primary sensory cor tex. The motor activation occurred consistently at the superior-most extent of the sensory activation within and across subjects. The sensory somatoto pic map of the human hand can be identified at 4 T High-resolution imaging at 4 T can be useful for detailed functional imaging studies.