RELATION OF CEREBELLUM TO UPPER BRAIN STEM

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Abstract
Internal structures of the upper brain stem of the cat were systemically explored following electrical stimulation of various areas of the cerebellum. Evoked potentials were especially prominent in 2 major systems of the brain stem, i.e., mesencephalic plus diencephalic tegmentum and many of the sensory relay nuclei of the thalamus. More variable responses were recorded from the mammillary bodies, hippocampus, globus pallidus, cerebral peduncle, superior colliculus and centromedial nucleus. Latency of response ranged within 3 groups: (I) short, 1 msec. or less, categorized as asynaptic; (II) medium between 1 and 3 msec; and (III) long, over 3 msec. but usually below 12 msec. Localized projections from anterior lobe, paramedian lobule, tuber vermis and ansiform lobule were observed, but data were not conducive to detailed analysis of these projections. The possible functional significance of a dual cerebellar projection, i. e., asynaptic and multisynaptic to related centers, is discussed as is a possible cerebellar role in the relay of various sensory modalities to the cerebrum.