Cerebral activation covaries with movement rate.

An important aspect in brain activation studies is the relationship between neuronal activity and measurable indices of function. We applied functional magnetic resonance imaging (fMRI) to investigate blood flow-related MR signal changes in response to different rates of repetitive movements of the index finger. The contralateral precentral gyrus and the posterior frontomesial cortex revealed a significant increase in MR signal over baseline for 1, 2 and 3 Hz finger movements, with a linear effect of rate in the precentral gyrus. Increased firing of neuronal 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 contribute to the activation pattern.