Functional organization of the anterior red necleus

Abstract

Single cell evoked potential activity were recorded in the anterior red nucleus, and interactions of responses to somatic, cortical, and dentate nucleus stimulation were examined. Clear evoked responses were present in the anterior red nucleus to stimulation of the four paws and the SI and SII cortices, whereas the motor and premotor cortices were only weakly represented. Most cells in the anterior red nucleus responded to stimulation of the paws and somatosensory cortex, but did not respond to stimulation of the motor cortex. In addition, cells which did respond to stimulation of the motor cortex were never influenced by dentate stimulation. It was concluded that there is no direct functional dependence between the cells of the posterior and anterior portions of the red nucleus. Monosynaptic evoked responses, composed of both a pre- and postsynaptic component, were recorded to contralateral dentate stimulation, and its response was only slightly modified by preceeding cortial or peripheral somatic stimulation. In contrast, the influence of dentate stimulation on cells in the anterior red nucleus was either direct excitation, inhibition, or a very weak facilitation on other responses, thus classifying the cells into three groups. Furthermore, these three groups of cells had different mean latencies to stimulation of the somatosensory cortex, thus suggesting a serial alignment. A model of cell interconnections in the anterior red nucleus was introduced and discussed.