Distribution of delta activity across nonrapid eye movement sleep episodes in healthy young men.
The distribution of delta activity across successive nonrapid eye movement (NREM) sleep episodes and its night-to-night stability across three consecutive nights were investigated by studying delta power with spectral analysis in 31 healthy young men. Repeated-measures analysis of variance (ANOVA) with polynomial contrast was applied to grouped data of absolute delta power and three indexes: (1) the rate of delta power per NREM episode to its duration, 2) the standardized rate for the last NREM episode, and 3) the logarithm of the standardized rate. A significant linear decrease across NREM episodes was observed for each variable in each successive night. In addition, using night as a second within-subjects factor, no night effect was observed. Yet, the subsequent analysis of the logarithmic data yielded greater F values in all three nights' data as well as a linear function that accounted for a greater proportion of total variance than the analysis of the nonlogarithmic data. Since a linear decline for the logarithm of a variable implies an exponential distribution for that variable, we conclude that delta activity is distributed exponentially across NREM episodes, and this finding shows a remarkable night-to-night stability.
Preud'homme
X A
XA
Department of Psychiatry, Erasme Hospital, Free University of Brussels, Belgium.
Lanquart
J P
JP
Mendlewicz
J
J
Linkowski
P
P
D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology; D003700:Delta Rhythm; D005583:Fourier Analysis; D006801:Humans; D008297:Male; D017286:Polysomnography; D012016:Reference Values; D012815:Signal Processing, Computer-Assisted; D012894:Sleep Stages / Q000502:physiology*