THE RETICULAR AROUSAL THRESHOLD DURING THE TRANSITION FROM SLOW-WAVE SLEEP TO PARADOXICAL SLEEP IN THE RAT

The short-lasting intermediate stage of sleep occurring between slow w ave sleep and paradoxical sleep showed frontal cortex spindles of high er amplitude and longer duration than during slow wave sleep, and hipp ocampal theta rhythm of lower frequency than during paradoxical sleep. During the intermediate stage, the mesencephalic reticular arousal th reshold was slightly higher than during the slow wave sleep and much l ower than in the paradoxical sleep. Thus, following this central react ivity test, the intermediate stage seems to be functionally nearer the slow wave sleep than the paradoxical sleep.