Hypothalamic temperature during the sleep cycle at different ambient temperatures.

Hypothalamic temperature during complete and incomplete sleep cycles (slow wave sleep followed by fast wave sleep and slow wave sleep followed by arousal, respectively) has been studied in freely moving cats at 20 degrees C and 0 degrees C ambient temperatures. The results show that sleep and thermoregulatory processes interact and, at 0 degrees C ambient temperature, become mutally exclusive. The occurrence of fast wave sleep is related to an opptimum range of hypothalamic temperatures which is specific in each enviromental conditions.