TEMPERATURE SENSITIVITY OF SLEEP HOMEOSTASIS DURING HIBERNATION IN THE GOLDEN-MANTLED GROUND-SQUIRREL

Brain temperature (T-br), vigilance state, and electroencephalograph s low-wave activity (EEG SWA, 1.0-4.0 Hz) were measured during hibernati on and spontaneous arousals to euthermia in seven golden-mantled groun d squirrels (Spermophilus lateralis). Animals were held at air tempera tures (T-a) ranging from 6 to 21 degrees C. SWA was used as a measure of the intensity of non-rapid eye movement (NREM) sleep. Squirrels tha t had hibernated at high T-a had lower SWA in NREM sleep in the hours following arousal than when they hibernated at low T-a. SWA in NREM sl eep during euthermia immediately following arousal was significantly c orrelated to minimum T-br and SWA during hibernation. The duration of the preceding hibernation bout had no significant effect on SWA during euthermia. We hypothesize that the restorative process of sleep, refl ected by SWA, is temperature sensitive and is compromised by the low t emperatures in hibernation. The accumulation of a SWA debt during hibe rnation may be related to the temperature-dependent depression of SWA during hibernation.