Period-amplitude analysis of rat electroencephalogram: effects of sleep deprivation and exercise

Electroencephalogram (EEG) wavelength and amplitude within NREM sleep, paradoxical sleep (PS), and wake were measured by computer in five intact rats and four rats with suprachiasmatic nucleus (SCN) lesions for the first recovery day following 24-h total sleep deprivation (TSD) achieved by keeping them on a rotating cylinder over water. To assess exercise effects, EEG within NREM was also analyzed in four intact rats for 8 h after separate 4-h TSD sessions at low and high rates of cylinder rotation (high rate = 12 times low rate). During recovery from 24-h TSD, EEG changed most dramatically in NREM. The number of slow waves per unit time (1-4 Hz wave incidence) and the amplitude at all wavelengths from 1 to 16 Hz were increased for up to 12 h and then fell below baseline levels for most of the next 12 h. Fast (5-16 Hz) wave incidence changed inversely with slow wave incidence. Wake and PS also showed initially increased amplitude, but shifts in incidence were from slow to fast waves. Relative to baseline, intact and SCN-lesioned rats showed similarly shaped recovery functions, indicating that EEG responses to sleep loss are largely independent of diurnal rhythms. Four-hour TSD at a low rotation rate affected NREM EEG similarly to 24-h TSD, but more mildly. The high rotation rate further increased slow wave incidence during recovery without further increasing slow wave amplitude. The results suggest that both EEG wave incidence and amplitude are responsive to prior wakefulness, but only incidence is responsive to prior exercise.