All animals showed bouts of hypothermia that became progressively deeper and longer as fasting progressed.  EEG and EMG were markedly affected by hypothermia, although the typical electrophysiological signatures of non-rapid eye movement (NREM) sleep, rapid eye movement (REM) sleep, and wakefulness enabled us to perform vigilance-state classification in all cases.  Consistent with previous studies, hypothermic bouts were initiated from a state indistinguishable from NREM sleep, with EEG power decreasing gradually in parallel with decreasing surface body temperature.  During deep hypothermia, REM sleep was largely abolished, and we observed shivering-associated intense bursts of muscle activity.



THERM