PRIOR SPONTANEOUS NOCTURNAL WAKING DURATION AND EEG DURING QUIET SLEEP IN INFANTS - AN AUTOMATIC-ANALYSIS APPROACH

To ascertain the role of spontaneous nocturnal waking duration on the EEG dynamics during quiet sleep (QS) periods, we analysed the nocturna l polygraphic recordings of 12 infants aged 9-47 weeks old. Their slee p was characterised by two sleep episodes, separated by spontaneous wa king and containing at least two QS-paradoxical sleep (PS) cycles each . Automatic analysis of the EEG activity recorded by the centro-occipi tal lead and reflecting the degree of synchronisation allowed us to co mpute a parameter whose values ranged from 0 (maximum of EEG synchroni sation) to 10 (maximum of EEG de-synchronisation). Three indicators of the time course of the parameter value were computed during the first QS period of the sleep episode subsequent to nocturnal waking: (i) th e parameter range (difference between the EEG parameter value at the Q S onset and that at the trough-maximum of EEG synchronisation); (ii) t he trough latency (time interval between QS onset and trough); and (ii i) rate of synchronisation (range/trough latency). These three indicat ors were the dependent variables in a multiple regression model, where the independent variables were age and the logarithm of the duration of prior waking. The parameter range was correlated with the duration of prior waking. Both the trough latency and the rate of synchronisati on were correlated with age only, respectively, positively and negativ ely. The marked decline in the rate of synchronisation throughout the first year of life could account for the failure to find a significant correlation between prior waking and the above indicator of the EEG d ynamics. The relationship between the duration of prior waking and the parameter range in following sleep in infants supports the hypothesis of the early emergence of the homeostatic regulation of sleep. (C) 19 98 Elsevier Science B.V. All rights reserved.