System for studying the topography of delta rhythm during sleep: further development.

A hybrid system for treatment of all-night sleep EEG records is described, which leads to the representation of sleep cycles by the continuous variation of the amplitude in a given frequency band. This system constitutes the development of a previous purely analogic one. The addition of a micro-processor and of a small computer renders the system far more flexible and easier to use. The results stored on tape are available for further treatments.

System for studying the delta rhythm during sleep and its topographical amplitude distribution.

An analogue system of processing all-night sleep EEG records which leads to the representation of sleep cycles by the continuous variation of the amplitude parameter in a given frequency band is described. The curves obtained are analogous to those resulting from more sophisticated computerized analyses. The cycles which they outline are in good concordance with those of the classic hypnogram. Moreover, the simplicity and the rapidity of the processing easily allow its application to multiple EEG channels. A topographical discrimination of the amplitude parameter during sleep was observed in normal subjecttion. The results obtained are illustrated in the case of a normal child and a young normal adult.

Topographical distribution of delta rhythms during sleep: evolution with age.

This study concerns the evolution of slow EEG activities (delta rhythms) and their topographical distribution during 31 night sleep records of 27 control subjects whose ages ranged from 1 month to 27 years. A system of data processing allows the representation of continuous changes in 8 derivations of the power of 0.5--4.5 c/sec waves. The obtained curves, whose respective magnitudes depend on the chosen montage, parallel the sleep cycles of the classical hypnogram. They do not clearly differentiate NREM sleep stages, but show a progressive increase of delta rhythm power with the deepening of NREM sleep. Moreover, measurement of the magnitude to these curves allows comparisons between the different channels in a given record and between different recordings. With the referential setting used in this study the topographical organization of the occipital, parietal and central curves proved occipital, parietal and central curves proved remarkably consistent in all subjects. The general magnitude of these curves decreased with age while that of frontal curves slightly increased. The right parietal curves were of greater magnitude than the left in every record obtained from children aged 2--5 years. The changes with age, and the intra- and interindividual differences are discussed. The data suggest hypotheses about the importance of NREM sleep in developmental processes.