fMRI evaluation of somatotopic representation in human primary motor cortex

We used fMRI to map foot, elbow, fist, thumb, index finger, and lip movemen ts in 30 healthy subjects. For each movement type confidence intervals of r epresentational sites in the primary motor cortex (M1) were evaluated. In o rder to improve the precision of their anatomical localization and to optim ize the mapping of cortical activation sites, we used both the assessment o f locations in the conventional 3D system and a 2D projection method. In ad dition to the computation of activation maxims of activation clusters withi n the precentral gyrus, centers of gravity were determined. Both methods sh owed a high overlap of their representational confidence intervals. The 2D- projection method revealed statistically significant distinct intralimb loc ations, e.g., elbow versus index finger movements and index finger versus t humb movements. Increased degree of complexity of finger movements resulted in a spread of the somatotopic location toward the arm representation. The ED-projection method-based fMRI evaluation of limb movements showed high p recision and was able to reveal differences in intralimb movement compariso ns. fMRI activation revealed a clear somatotopic order of movement represen tation in M1 and also reflected different degrees of complexity of movement . (C) 2000 Academic Press.