Delta (0.5-1.5 Hz) and sigma (11.5-15.5 Hz) EEG power dynamics throughout quiet sleep in malnourished infants

The present study aimed to quantify, through power spectral analysis, the d ynamics (temporal pattern and temporal interrelationship) of the the EEG po wer in the low-delta (Delta) and in the sigma-spindle (sigma) frequency ban d during quiet sleep (QS) in 5 malnourished infants (MI), 5.5 to 13.5 month s old, and in 5 age-matched healthy control infants (CI). Malnutrition resu lts in modification of the temporal pattern of Delta and sigma band power d uring QS. The Delta band power increases faster in MI than in CI, leading t o higher power levels in MI at the same time segment. However, the overall trend of the Delta band power throughout QS is similar in MI and CI. The pr emature ending of QS phases (uninterrupted QS periods), and the reduced tot al amount of QS which have been reported in MI could result in an increased slow wave sleep (SWS) "pressure". This SWS pressure could account for both the higher level and the faster increase of the Delta band power during th e QS phase which are found in MI when compared to CI. (C) 1999 John Wiley & Sons, Inc.