THE EFFECT OF MOVEMENT FREQUENCY ON CEREBRAL ACTIVATION - A POSITRON-EMISSION-TOMOGRAPHY STUDY

Knowledge of the effect of performance frequency on activation of moto r areas in positron emission tomography (PET) studies is crucial to th e interpretation of experiments in which performance is a variable. We studied this effect in six normal right-handed volunteers using (H2O) -O-15 PET to measure regional cerebral blood flow (rCBF). Subjects wer e scanned at rest and while executing joystick movements with the righ t hand in freely chosen directions at different frequencies. Significa nt frequency dependent increases in rCBF were demonstrated in contrala teral sensorimotor cortex, lateral premotor cortex bilaterally, poster ior supplementary motor area (SMA), and ipsilateral cerebellar hemisph ere and vermis. The striatum and the right dorsal prefrontal cortex we re also activated by joystick movement compared with rest, but the mag nitude of activation found in these areas was independent of the frequ ency of movement. The results suggest that primary motor cortex, poste rior SMA, lateral premotor cortex and cerebellum are involved in deter mining the basic parameters of movement. Frequency dependent activatio n in these areas suggests phasic activity related to movement. In cont rast, activation of the dorsal prefrontal cortex and the striatum is n ot frequency dependent. This may reflect continuous rather than phasic activity in these areas during the task and suggests their role is no t simply related to movement execution but higher level during this fr ee selection joystick task. (C) 1997 Elsevier Science B.V.