RATE DEPENDENCE OF REGIONAL CEREBRAL ACTIVATION DURING PERFORMANCE OFA REPETITIVE MOTOR TASK - A PET STUDY

Using repeated positron emission tomography (PET) measures of regional cerebral counts, we investigated the regional cortical activations in duced in eight normal subjects performing eight different frequencies of fingertapping (0.5-4 Hz) with the right index Finger. The task was auditorially cued and the performance recorded during the scanning pro cedure. Performance evaluation showed increased error rates, during fi ngertapping. of high and low frequencies, and the best tapping perform ance was measured in the midrange of frequencies. Significantly activa ted areas (p < 0.05) of normalized cerebral counts were located in the left sensorimotor cortex (MIS1), right motor cortex, left thalamus, r ight insula, supplementary motor. area (SMA), and bilaterally in the p rimary auditory cortex and the cerebellum. Statistical evaluation show ed a significant (p < 0.01) and positive dependence of cerebral activa tion upon movement rate in the contralateral MISI. There was no signif icant rate dependence of cerebral activation in other activated motor areas. The SMA and the right cerebellar hemisphere showed a more unifo rm activation throughout the tapping frequency range. Furthermore, we found a stimulus rate dependence of cerebral activation in the primary auditory cortex. We believe that the present data provide useful info rmation for the preparation and interpretation of future motor activat ion studies of normal human subjects and may serve as reference points for studies of pathological conditions.