A new vestibular thalamic area: Electrophysiological study of the thalamic reticular nucleus and of the ventral lateral geniculate complex of the cat

Abstract

Single unit recordings were carried out in the reticularis thalamic nucleus (RT) and the ventral lateral geniculate body (LGv) of chronically prepared alert cats under sinusoidal vestibular stimulation in the horizontal plane. Optokinetic stimulation was also used. Of the 57 recorded neurons, 12 present vestibular modulation in the dark, analogous to Duensing's and Schaefer's (1958) type I response in the vestibular nuclei. Responses of 26 cells are similar to response of type II vestibular neurons and 14 units have a type III response; the 5 remaining cells were activated by vestibular stimulation in the vertical sagittal plane. The majority of these cells does not present detectable direct visual responses, but 50% can be driven by optokinetic stimulation. 74% of types I, II and III neurons show saccadic resonses to vestibular nystagmic saccades in the dark. About 60% present similar saccadic modulations during optokinetic nystagmus and 55% keep this response for spontaneous saccades in the dark or in front of a striped background. The saccadic responses are constant for a given neuron in all cases of stimulation with latencies ranging from 30 msec prior to the beginning of the saccade to 120 msec after its onset. The histological localization of these units falls on one hand into the caudal part of the RT nucleus (type III neurons) above the dorsal lateral geniculate nucleus and on the other hand within the internal subdivision of the LGv and its rostral limit (all other types). The significance of this new, saccadic and vestibular focus in the feline thalamus is discussed in relation with the two previously known vestibular thalamic relays in terms of interrelations between the vestibular and the visual systems.

Corollary discharge: Its possible implications in visual and oculomotor interactions

“…In the cat, the work of the above mentioned authors [85], recently confirmed by MAGNIN and PUTKONE~ [86], showed that 50 o,~ of the recorded LGv cells modified their activity in relation to saccades, but do not present any response to visual stimuli. This is confirmed by the fact that the saccadic response is the same whether the saccade is made in the dark or in front of an illuminated pattern.…”

“…The characteristics of the saccadic responses are different from those recorded in the monkey PGN: particularly, in the cat, a significant number of neurons begin to respond about 30 msec prior to the onset of the saccade. Finally, a strong vestibular input has been shown in the cat LGv [22,85,86], affecting the saccadic cells, but not the visual ones. Such a vestibular input could not be found in PGN neurons [87].…”

The thalamocortical vestibular system in animals and humans

“…In the lateral geniculate nucleus (LGN) of the cat, Magnin and Putkonen (1978) recorded vestibular neurons responding to horizontal or vertical angular stimulation. Neurons activated by the stimulation of the posterior semicircular canals (pitch rotations) were found in the LGN (Matsuo et al, 1994).…”

“…Only few studies investigated thalamic responses to head movements, and most have focused on responses to head rotations in the yaw plane (Büttner and Henn, 1976;Büttner et al, 1977;Magnin and Fuchs, 1977;Magnin and Putkonen, 1978;Meng et al, 2007), more rarely in the pitch plane (Matsuo et al, 1995). A recent electrophysiological study by Meng et al (2007) in macaque monkeys described the dynamics of vestibular neurons during roll, pitch and yaw head rotations, as well as during horizontal translations (Fig.…”

“…Type III neurons are activated during rotations ipsilateral and contralateral to the recording site. Most of the neurons responding to yaw rotations were of type II in the VP thalamus (Marlinski and McCrea, 2008b), as well as in the LGN and reticularis thalamic nucleus (Magnin and Putkonen, 1978).…”