Patterning of NREM sleep periods in normals: an observation revisited

Both the visual examination of all-night sleep recordings in both normals and patients, generated by a delta wave analyzer, and spectral analysis have suggested that delta wave sleep often appear to rise gradually during a NREM period and then to cease abruptly. Such observations by minute-by-minute computer plots of delta wave activity have strengthened the notion of a REM generator and/or a delta sleep generator in the central nervous system. We now report observations on a sample of 23 normal subjects under the age of 45 in which we investigated the 'rise and fall' of delta sleep activity during successive NREM periods. For these 23 normal subjects, significantly greater maximal decreases throughout the night were noted in each of these 4 NREM periods as compared to the maximal increases. Furthermore, these findings have implications for the understanding of the physiology of sleep and particularly the on- and off-generator of REM and NREM sleep.