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). LS1 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.