CEREBRAL ACTIVATION COVARIES WITH MOVEMENT RATE

AN important aspect in brain activation studies is the relationship be tween neuronal activity and measurable indices of function. We applied functional magnetic resonance imaging (fMRI) to investigate blood flo w-related MR signal changes in response to different rates of repetiti ve movements of the index finger. The contralateral precentral gyrus a nd the posterior frontomesial cortex revealed a significant increase i n MR signal over baseline for 1, 2 and 3 Hz finger movements, with a l inear effect of rate in the precentral gyrus. Increased firing of neur onal aggregates or recruitment of additional neuronal units within the primary motor cortex necessary for increased output to target neurons and maintaining posture of nearby distal and proximal joints may cont ribute to the activation pattern.