Two Types of Light Sleep and Central Visual Function in Cats

Abstract

Using cats carrying permanent electrodes, the central visual function was studied during the three phases of natural sleep (LS1, LS2, and DS). LS, and LS2 are the phases of light sleep (high-voltage slow wave sleep); LS1 is characterized by spindle activity and occasional desynchronized activity of the sensorimotor cortical EEG, whereas during LS2 slow waves are predominant. DS corresponds to so-called deep sleep (low-voltage fast wave sleep).1. Sensorimotor cortical and hippocampal electrographic signs of the three phases of sleep were studied quantitatively by means of an automatic frequency analyser.2. It was shown during a long course of sleep-wakefulness cycle that the three phases of sleep could be identified with a good accuracy not only on the basis of the cortical and hippocampal EEGs but also by observing spontaneous activities of the lateral geniculate body (LGB) and posterior neck muscles.3. Antidromic responsiveness of the optic tract (OT) terminals was always highest during DS and decreased from LS1 to LS2 4. Orthodromic responsiveness of the OT terminals was minimum during DS and increased from LS1 to LS2. Sometimes, the responsiveness during DS was highest and decreased from LS2 to LS1.5. Postsynaptic responsiveness of the LGB was highest during DS. The lowest responsiveness was seen in some cases during LS1 and in others during LS2.6. Action of spontaneous spiky waves of the LGB (phasic activity of Jouvet) upon pre and postsynaptic responsiveness of the LGB was studied during LS2 and DS. Suppression of the orthodromic responsiveness of the OT terminals and facilitation of the postsynaptic LGB neurons were seen equally in the two phases of sleep.7. Responsiveness of the visual cortex tended to be highest during LS2 and to decrease from DS to LS1. Fluctuation of the responsiveness was very marked during LS2.Many workers have presented ample evidence that synaptic transmission and neuronal excitability at the cortical and subcortical levels are modified during the sleep-wakefulness cycle of freely behaving animals.

Spontaneous and Evoked Unitary Activities of Cat Lateral Geniculate Neurons in Sleep and Wakefulness

“…The facilitation associated with the negative phase makes a great contribution to enhance the average discharge rate of the P units during deep sleep . This is also correlated with the previous finding by IWAMA and his associates that synaptic transmission at the LGB , seen at the level of mass activity, is temporarily facilitated in the presence of the DSWs (The observations of these workers were made without a distinction of the positive and negative phases of the DSWs)2e, 21,25,33). The evidence in the same line has been presented that the cellular component of the antidromic mass response of the LGB increases in amplitude while the DSWs are showing negative deflections19) .…”

“…They also noted that during deep sleep the transmission at the LGB suffers a transient facilitation when the otherwise desynchronized background activity yields the spiky waves20, 21,25,33) which have been called "deep sleep waves" (DSWs) by BROOKS and BIZZI8),"phasic activities" by M. JouvE24) or "LGB spikes" by MIKITEN et al 27) That modification of synaptic transmission of the LGB during sleep and wakefulness is not limited to the postsynaptic level but also extended to the presynaptic terminals of the optic tract fibers has been wellestablished20,25). It was shown that the presynaptic inhibition is developed most strongly during deep sleep and decreases from arousal to light sleep.…”