Figure 4

VARYING RHYTHMS are identified with the various states of sleep. From left to right, a wakeful cat (I ) shows high speed alternations in electric potential in both cortical and subcortical regions of the brain, as well as neck-muscle tension. In light sleep (2) the cat shows a slower rhythm in the traces from the cortical and sub cortical regions, but neck-muscle tension continues. The phasic, or periodic, aspects of paradoxical sleep (3) are marked by isolated spike discharges from the rear of the cortex and the pons, as well as by rapid eye movement and limb movements. Loss of neck-muscle tension is a tonic (4) rather than a phasic phenomenon. Other tonic, or continuous, aspects of paradoxical sleep are high-speed cortical rhythms and regular "theta" waves from hippocampus.

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