FMRI STUDIES OF THE SUPPLEMENTARY MOTOR AREA AND THE PREMOTOR CORTEX

Brain activation patterns associated with three motor tasks, differing in the mode of movement selection, were studied in seven right-handed subjects, using functional magnetic resonance imaging (fMRI). The tas ks consisted of sequences of finger movements in which the next finger was selected (i) according to a fixed sequence (FIX), (ii) in respons e to an external sensory cue (RAND), or (iii) on the basis of free, in ternal selection (SELF). Periods of hand relaxation (REST) alternating with the tasks served as a control. Functional maps resulting from co mparison of the motor tasks with REST reveal activation in primacy sen sorimotor cortex, medial and lateral premotor areas, cingulate cortex, and parietal cortex. The task activation level, defined as the percen tage MR signal increase for each task relative to REST, and the differ ential activation, defined as the percentage MR signal increase for RA ND and SELF relative to FIX, were calculated in each area. All areas s howed a higher activation level for RAND and SELF than for FIX. A sign ificant difference in activation level or differential activation betw een SELF and RAND was found in the posterior part of the superior fron tal sulcus, in a part of the premotor cortex on the lateral brain surf ace, in the anterior cingulate motor cortex, and in the posterior part of the superior parietal cortex. The high-resolution and single-subje ct approach, provided by fMRI, allowed the distinguishing of multiple foci in medial frontal areas, premotor cortex, and parietal cortex, re flecting the functional heterogeneity of these areas suggested by prev ious studies. (C) 1997 Academic Press.