Sleep-related variations of membrane potential in the lateral geniculate body relay neurons of the cat

Membrane potential of lateral geniculate body relay neurons was monitored in chronic cats during the sleep-waking cycle. Neurons were tonically depolarized throughout paradoxical (P) sleep and the maximal level of polarization occurred during slow (S) sleep (mean difference of membrane potential between S and P sleep:+ 10.2 ± 1.3mV, n= 6,range: 8–12mV). Some features of the spontaneous activity of S and P sleep are briefly discussed in relation to the level of membrane potential. In particular it is suggested that the phasic depolarizations underlying the bursts of action potentials during S sleep, and which are reproduced by injection of inward currents could be caused by afferent impulses from retinal cell axons impinging upon the hyperpolarized membrane.