Fig. 2.

Intracellular activity of neocortical neuron during three major states of vigilance in a chronically implanted, nonanesthetized cat. High-amplitude and low-frequency field potentials, intracellular cyclic hyperpolarizing potentials, and stable muscle tone are distinctive features of SWS. Low-amplitude and high-frequency field potential oscillations, tonic neuronal firing with small fluctuations in the membrane potential, rapid eye movements, and muscle atonia are cardinal features of REM sleep. There is a slight hyperpolarization during REM-related ocular saccades. Low-amplitude and high-frequency field potential oscillations, tonic firing with smaller fluctuations in the membrane potential, and muscle tone with periodic contractions are characteristics of the waking state. The parts indicated byarrows are expanded below. At bottom are histograms of membrane potential distribution during three states of vigilance. Histograms were constructed by sampling of neuronal activity at 10 kHz and counting the number of samples with bins of 0.5 mV.