The human red nucleus and lateral cerebellum in supporting roles for sensory information processing

A functional MRI study compared activation in the red nucleus to that in th e lateral cerebellar dentate nucleus during passive and active tactile disc rimination tasks. The study pursued recent neuroimaging results suggesting that the cerebellum may be more associated with sensory processing than wit h the control of movement for its own sake. Because the red nucleus interac ts closely with the cerebellum, the possibility was examined that activity in red nucleus might also be driven by the requirement for tactile sensory processing with the fingers rather than by finger movement alone. The red a nd dentate nuclei were about 300% more active (a combination of activation areas and intensities) during passive (non-motor) tactile stimulation when discrimination was required than when it was not. Thus, the red nucleus was activated by purely sensory stimuli even in the absence of the opportunity to coordinate finger movements or to use the sensory cues to guide movemen t. The red and dentate nuclei were about 70% more active during active tact ile tasks when discrimination was required than when it was not (i.e., for simple finger movements alone). Thus, the red nucleus was most active when the fingers were being used for tactile sensory discrimination. In both the passive and active tactile tasks, the observed activation had a contralate ralized pattern, with stronger activation in the left red nucleus and right dentate nucleus. Significant covariation was observed between activity in the red nucleus and the contralateral dentate during the discrimination tas ks and no significant correlation between the red nucleus and the contralat eral dentate activity was detected during the two non-discrimination tasks. The observed interregional covariance and contralateralized activation pat terns suggest strong functional connectivity during tactile discrimination tasks. Overall, the pattern of findings suggests that the activity in the r ed nucleus, as in the lateral cerebellum, is more driven by the requirement s for sensory processing than by motor coordination per se. (C) 2000 Wiley- Liss, Inc.