Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Event-related potential studies in man suggest a role for the supplementary motor area (SMA) in movement preparation, particularly when movements are internally generated. In a previous study combining PET with recording of movement-related cortical potentials, we found similar SMA activation and early pre-movement negativity during self-initiated and predictably paced index finger extensions. Early pre-movement negativity was absent when finger movements were paced by unpredictable cues. We postulated that preparation preceding self-initiated and predictably cued movements was responsible for equivalent levels of SMA activation in these two conditions. To test this, we have performed further studies on six normal volunteers with H2(15)O-PET. Twelve measurements of regional cerebral blood flow were made in each subject under three conditions: rest; self-initiated right index finger extension at a variable rate of once every 2-7 s; and finger extension triggered by pacing tones at unpredictable intervals (at a rate yoked to the self-initiated movements). Activation associated with these conditions was compared using analysis of covariance and t statistics. Compared with rest, unpredictably cued movements activated the contralateral primary sensorimotor cortex, caudal SMA and contralateral putamen. Self-initiated movements additionally activated rostral SMA, adjacent anterior cingulate cortex and bilateral dorsolateral prefrontal cortex (DLPFC). Direct comparison of the two motor tasks confirmed significantly greater activation of these areas and of caudal SMA in the self-initiated condition. These results, combined with our previous data, suggest that rostral SMA plays a primary role in movement preparation while caudal SMA is a motor executive area. In this experiment and in our earlier study, DLPFC was activated only during the self-initiated task, in which decisions were required about the timing of movements.


Journal article



Publication Date



123 ( Pt 6)


1216 - 1228


Adult, Animals, Cerebrovascular Circulation, Fingers, Humans, Male, Middle Aged, Motor Cortex, Movement, Prefrontal Cortex, Psychomotor Performance, Rest, Tomography, Emission-Computed, Volition