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Neuronal activity in the vestibular nuclei after trigeminal stimulation
No full textThe activity of 131 vestibular neurons was investigated in 40 guinea pigs during trigeminal stimulation. The influence of trigeminal sensory information was tested by means of electrical stimulation of the trunk of the trigeminal nerve and with nonnociceptive cutaneous stimulation of facial areas. The spontaneous activity of vestibular neurons was modified by trigeminal electrical stimulation with an increase or decrease of the discharge rate. Some units underwent rhythmic modulation. Forty-one percent of recorded units responded also to cutaneous trigeminal stimulation. An analysis of vestibular action potentials evoked by trigeminal stimulation revealed latency values from 1.2 to 6.2 ms. The anatomic-functional relationship between the trigeminal and the vestibular systems is discussed in light of the reported results
Optic nystagmus and vestibular nuclei: Unitary activity of vestibular neurons during nystagmus
No full textThe behavior of 102 vestibular neurons during optic nystagmus was investigated in 25 guinea pigs with extracellular microelectrodes. The recorded vestibular neurons were electrophysiologically identified by their orthodromic response to ipsilateral labyrinthine stimulation and by antidromic activation of the medial longitudinal fascicle. Of the 102 recorded units, 92 were modulated by the electrical stimulation of at least one optic nerve. The presence of vestibular neurons sensitive to the direction of nystagmus induced by labyrinthine or optic stimulation was also analyzed
Optic nystagmus and vestibular nuclei: Effects of vestibular nuclear ablation and interaction phenomena between optic and labyrinthine responses
No full textIn 20 guinea pigs, eye nystagmus of visual origin was investigated following stimulation of an optic nerve (optic nystagmus). The interactions between vestibular and visual inputs were observed by eliciting optic and labyrinthine nystagmus simultaneously. After complete removal of the vestibular nuclei, optic nystagmus was tested: It was no longer elicitable. On that basis, it is possible to conclude that the vestibular nuclei represent an essential station in the mechanism of optic nystagmus
Neural discharge of medial geniculate body units and single semicircular canal stimulation
No full textIn curarized guinea pigs, 68 neurons of the medial geniculate body (MGB) were tested with vestibular and acoustic stimulations. Single semicircular canals were stimulated thermally. Convergence of acoustic and vestibular afferences on the same MGB unit was observed. Following stimulation of the semicircular canals, activation and inhibition of unitary discharge were recorded, inhibition being predominant, while, when clicks were delivered, bursts of activity occurred. The implications of MGB in vestibular and acoustic integration are postulated
Diazepam enhances cerebellar inhibition on vestibular neurons
No full textThe spontaneous neuronal activity of the lateral (LVN) and the superior (SVN) vestibular nuclei was analysed before and after the intravenous (i.v) injection of diazepam in 'encephale isole', decerebrate and cerebellectomized rabbits. The inhibition of vestibular neurons was dependent on the integrity of cerebellar connections with LVN, while these links were partially responsible for the diazepam inhibition on SVN. A role of spinal and telediemesencephalic structures was not recognized. Considering that diazepam does not increase the activity of Purkinje cells, the drug effect ought to be exerted at the level of the Purkinje cell junctions with the cerebellar nuclei and with the vestibular neurons. GABA being the neurotransmitter released the Purkinje cells evidence is provided for a diazepam potentiation of the GABAergic mechanism at the level of vestibular system
Individual semicircular canals and pontine reticular units
No full textIt can be claimed that, although pontine reticular formation (RF) neurons are related to the ocular quick movements, only some units are responsible for the nystagmic rhythm. It can also be concluded that reticular units are involved in three different types of ocular nystagmus. Thus, according to experiments in guinea pigs pontine RF seems to be related not only to horizontal nystagmus, as claimed up to now, but also to vertical nystagmus
Trigeminal stimulation modulates vestibular unitary activity
No full text139 vestibular neurons were analyzed in 38 guinea-pigs after the stimulation of trigeminal fibers: increase or decrease of discharge rate and also rhythmic modulation of vestibular unitary activity were observed
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