Remarkable similarities between the temporal organization of neocortical electrographic sleep patterns of rats and humans

RESUMO

Electrocorticographic activity was automatically recorded in albino rats for 72 consecutive h and analyzed by procedures suitable to detect 24-h rhythms. Beta (alert wakefulness), theta (somnolence), delta (slow wave sleep) and sigma 1 (superficial synchronized sleep) activities showed a robust circadian rhythmic distribution. The acrophases (maxima of the adjusted cosine curve) occurred at 2339, 0759, 0837 and 1325 h, respectively. EMG atonia and extreme hypotonia (less than 10% of mean EMG level) episodes showed a 24-h rhythm peaking at 1418 h. The temporal sequence within the circadian rest period, i.e., somnolence, slow, wave sleep, superficial synchronized sleep and paradoxical sleep, is very similar to that known to occur during the nocturnal sleep of humans