Cyclic Delta Peaks During Sleep: Result of a Pulsatile Endocrine Process?

To the Editor.— It has long been Known¹,²that the integrated amplitude of delta (0 to 3 Hz) electroencephalogram (EEG) waxes and wanes across sleep, presenting a series of peaks (high EEG synchrony) and troughs (low EEG synchrony). The amplitude of the peaks declines across sleep, albeit not uniformly (see below). The tops of the early peaks are scored visually as stage 4, and the troughs are scored as stage 2 or rapid eye movement (REM) throughout. The peak-trough pattern is a naturalistic expression of the sleep EEG, unbiased by the assumptions and constraints of visual stage scoring. While some characteristics of these patterns have been described,¹⁻⁴as far as we know, peaktrough curves have not previously been measured as the dependent variable in experimental sleep studies. We have now carried out such measurements, reexamining data from a recent study⁵of total sleep deprivation (TSD); TSD is