par Steriade, Mircea;Stoupel, Nicolas 
Référence Electroencephalography and clinical neurophysiology, 12, 1, page (119-136)
Publication Publié, 1960-02
Référence Electroencephalography and clinical neurophysiology, 12, 1, page (119-136)
Publication Publié, 1960-02
Article révisé par les pairs
| Résumé : | 1. 1. The authors studied in "encéphale isolé" or in chloralosed cats convergence and the reactional interference between cortical responses to specific auditory stimuli (clicks, electric shocks to the medial geniculate body) and the cortical potentials produced by the stimulation of the auditory area of the cerebellum. Simultaneously an attempt was made to identify the pathways by which the auditory impulses are transmitted from the cerebellum to the cerebral cortex. 2. 2. The cortical responses to cerebellar shocks recorded in the secondary auditory area (E.p.i.), responses whose latencies are longer than those of the primary area, are not relayed by the latter. Strichninization of a cortical point of the primary area does not influence the response of the secondary area to cerebellar shocks in contrast to a response in the same area as produced by clicks. In addition, a cortical incision which separates the two auditory areas does not abolish the response of the secondary area to cerebellar shocks. 3. 3. Conditioning of the response to the click by a preceding shock to the cerebellum always reduced the cortical potential evoked by the click. This occlusion was very marked at all intervals between 10 msec. and 70 msec. decreasing progressively as the interval augmented in duration. In special experimental conditions where the response to the click was followed by secondary late waves the conditioning cerebellar shock extinguished the secondary wave even after an interval of 400 msec. The occlusion of the response to the click occurred even with conditioning cerebellar shocks which themselves were unable to produce a visible cortical response. The inverse combination in which the click preceded the cerebellar shock produced with the same intervals the same effects, i.e. a depression of the response to the cerebellar shock by the conditioning click. 4. 4. The same phenomenon of occlusion was observed also with the potential evoked by an isolated shock applied to the medial geniculate body preceded by a conditioning cerebellar shock. 5. 5. In none of our experiments was there a response in the medial geniculate body to a cerebellar stimulus. Correlated to this is the observation that occlusion of the cortical response to the click by the cerebellar shock was not accompanied by the occlusion of the response in the medial geniculate body to the same sensory stimulus. 6. 6. On the other hand a response to a cerebellar shock could be observed in the reticular formation and this reticular response produced occlusion of the reticular response produced by the click. 7. 7. Bi-lateral electrolytic destruction of the medial activating mesencephalic system was unable to produce disappearance of the response in the primary auditory area evoked by a cerebellar shock, but produced an abolition of the evoked potentials in the secondary area (E.p.i.) and at the same time also extinguished the responses obtained beyond the auditory area due to a diffusion process engendered by chloralose. The same effect could be produced by a unilateral lesion of the medial activating system if it was placed homolateral to the cortical areas recorded from. Destruction of the homolateral red nucleus produced no disappearance of the potential record in the sigmoid gyrus in response to a cerebellar stimulus, this response being due to the diffusion process produced by chloralose. The fact that destruction of the reticular formation prevents propagation of the cerebellifugal impulses into the secondary auditory area and into other non-auditory cortical areas while at the same time leaving intact the response in the primary auditory area tends to confirm the hypothesis according to which the dynamogenic diffuse projection upon the cerebral cortex is transmitted by a pathway passing through the reticular formation. On the other hand the cerebello-cortical impulses which project to the primary auditory area do not seem to involve a relay in the medial geniculate body. © 1960. |
