AN FMRI STUDY OF THE HUMAN CORTICAL MOTOR SYSTEM RESPONSE TO INCREASING FUNCTIONAL DEMANDS

Functional magnetic resonance imaging (fMRI) was used to study activat ion changes in the human primary motor-sensory areas (MAs), supplement ary motor areas (SMAs), premotor areas (PMAs) and the superior and inf erior parietal areas (SPAs, IPAs) during right hand finger movements a s the rate, force and complexity of movement were varied, A preliminar y reproducibility study of a single subject doing the same repetitive index finger movements in nine different sessions over a six week peri od demonstrated highly consistent and highly localized activation in t he contralateral MA. ANOVAs demonstrated highly significant main effec ts of increasing the force and complexity of movement, thereby illustr ating the distributed and integrated systemic character of the cortica l motor system, Interactions between brain region and the rate and com plexity of movements suggested functional specialization of some compo nents of the system, Increasing the rate of movement led to increased activity only in the contralateral MA; increasing complexity led to gr eater increases in activity in the left and right SPAs and the left IP A than in other areas, Although activation was evident in varying degr ee throughout the multiple motor areas, only the MAs showed consistent lateralization of activation. (C) 1997 Elsevier Science Inc.