Symposium on the Role of the Vestibular Organs in Space Exploration (1970) / Chapter Skim
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EVOKED POTENTIAL AND MICROELECTRICAL ANALYSIS OF SENSORY ACTIVITY WITHIN THE CEREBELLUM
EVOKED POTENTIAL AND MICROELECTRICAL ANALYSIS OF SENSORY ACTIVITY WITHIN THE CEREBELLUM
Pages 245-258
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From page 245... ...
Sensory impulses arising from the tail region of the animal are located adjacent to the vestibular system. As the sensory areas representing the surface of the animal spread out on the dorsal surface, the two face areas overlap.
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5 and 7) showed direct fibers from flocculonodular lobe to the lateral and medial vestibular nuclei.
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Since it is difficult to find overlapping pathways in these two systems, it is not unreasonable to assume that there is overlapping within the cerebellar cortex. Furthermore, as shown in figure 4, there is interaction of impulses arising in the auditory area of the cerebrum and click-induced impulses within the auditory area of the cerebellum, with a recovery time between conditioning and test stimuli of as much as 400 msec when Chloralosane anesthetic was used.
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Note overlapping areas of visual and auditory responses and the shorter recovery time when Flaxedil medication was used.
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RESULTS In figure 8 is shown a series of traces recorded from the auditory area of the cerebellum when a single shock was applied directly to the auditory branch of the eighth nerve. The recording electrode was adjacent to the Purkinje-cell layer, and the high-amplitude units appear to represent discharges of individual Purkinje cells.
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C: Evoked responses in cerebrum resulting from surface stimulation of most posterior folium of pyramis (20 V, 1.0 msec)
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In 9B are shown the results of stimulating the pial surface of an adjacent folium and the induction of inhibition of Purkinje-cell activity in the tuber vermis for 200 msec. There are several explanations for this; however, the one we favor is the inhibition induced by the Purkinje-cell axon collateral which passes from one folium to an adjacent folium and induces relatively short inhibition directly on other Purkinje cells.
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This is followed by a period about 600 msec long in which there is inhibition of the higher voltage single units observed in the prestimulatory period which, because of the amplitude and the electrode tip location, were assumed to be Purkinje cells. As shown by Eccles et al.
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Thus, unlike the cerebral cortex, the cerebellar cortex possesses intrinsic activity which varies little from area to area. At this point a fundamental question may be asked.
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In figure 12, note that the burst of fast activity in nucleus fastigii precedes slightly the slow wave in vermis which occurs during point of reversal; i.e., point of zero acceleration. Additional data show that changes in the activity of the fastigial nuclei are time locked to changes in the activity of the medial vestibular nucleus related to the fast phase of horizontal nystagmus.
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The fourth trace shows EEG recording from left thalamocortical radiations (LTCR) , and the fifth trace shows EEG record taken from left nucleus fastigii (LNF)
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30) which showed the direct inhibitory action of Purkinje cells on cells in the lateral vestibular nucleus, as well as the indirect effect of Purkinje cells on nucleus fastigii, thence to cells in lateral vestibular nucleus.
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3. INGVAR, S.: Zur Phylo- und Ontogenese des Kleinhirns nebst einem Versuche zu einheitlicher Erklarung der zerebellaren Funktinn und Lokalisation.
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The cerebellar projection passes through the dorsal aspect and synapses in the nucleus fastigii. From the nucleus fastigii it goes forward in the brachium conjunctivum to the anterior medial zone of the medial geniculate body.
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