| Research Abstract |
Intact adult cats and juvenile Japanese monkeys (M. fuscata) were the subject of this study. In cats, a stimulating microelectrode was implanted targeting cerebellar locomotor region (CLR), which corresponds anatomically to the midline of hook bundle of Russel, through which multiple ascending and descending fastigiofugal fibers decussate. In an unrestrained, awake cat, a train pulse CLR microstimulation (200 Hz) evoked fore- and hindlimb well coordinated quadrupedal (Q) locomotion. After making a microlesion at the CLR site, the cat could still walk spontaneously but with considerably impaired coordination of fore- and hindlimb movements. We consider that CLR stimulation resulted in an activation of multiple fastigiofugal fibers descending bilaterally to the brainstem, thus simultaneously exciting cells of origin of major descending motor pathways, and that CLR lesion interrupted transmission of locomotor driving signals originating from the fastigial nucleus (FN) to locomotor-related brainstem-spinal cord mechanisms. In a single monkey walking either quadrupedally or bipedally, we have identified active brain regions by PET. During execution of Q and bipedal (B) locomotion task, we found that neuronal activities at multiple but different brain regions of the cerebellum, visual and motor cortices were enhanced. The results demonstrated that functional significance of visuomotor coordination is stronger during execution of B locomotion than that during execution of Q locomotion, and that in the latter, the cerebellum plays a major role. Based on the results obtained, we propose a new working hypotheis that the FN, with it s unique multiple and parallel output pathways, is one of the supraspinal centers involved in the initiation and control of 0 and B locomotion in both cat and monkey.
|
