Reticular control of thalamic transmission during behavioral states: A study in dorsal lateral geniculate nucleus relay neurons of the cat

Abstract

In behaving cats adapted to head restraint we examined the changes of spontaneous activity of dorsal lateral geniculate relay neurons provoked by weak stimulation of mesencephalic reticular formation during different states of sleep and alertness. The neurons were classified as fast- and slow-conducting neurons depending on their optic tract latency. When the reticular stimulation was delivered during slow-wave sleep, it increased the firing rate principally in slow neurons and suppressed the burst pattern. The increases occurred on a long depolarization in intracellular recordings ( n = 9). The effect resembled one that was simultaneous with pontogeniculooccipital waves. Only slow neurons showed a correlation between the relative increases and the prestimulus firing rate. The excitatory effect was reduced and less frequent during wakefulness and paradoxical sleep in both latency groups. When reticular stimulation did not influence the spontaneous activity of the activated states, it also did not modify the optic tract-elicited hyperpolarization. The data tend to demonstrate that the efficiency of the reticular stimulation depends principally on the rat and pattern of the spontaneous activity which, itself, varies largely according to the behavioral state and moderately according to the optic tract latency.