Delta component variations in human sleep electroencephalogram.

All night sleep was recorded polygraphically on 14 healthy adults, once for each person, and EEG was analyzed with bandpass filters. The integrated values during successive 10 second epochs were recorded consecutively at 1 mm intervals, separately for each frequency band. The variations of integrated values for long time span were clearly observed. The findings on 1-2 Hz component are reported exclusively in this report. (1) Four variation patterns were classified on the variations of integrated values of 1-2 Hz band component; long undulation, short undulation, irregular undulation and slight fluctuation. Short undulation was superimposed on long undulation. Long undulation had a gradually increasing slope, a plateau and steeply decreasing slope. Irregular undulation showed generally irregular fluctuations, without any definite variation patterns. During slight fluctuation the variations were small. Long undulation and irregular undulation corresponded to slow-wave sleep and slight fluctuation corresponded to REM sleep. The mean duration of each long undulation and irregular undulation was 31.2 and 11.9 minutes, respectively. In long undulations, 62.8% of the time was occupied by Stage 2 and the lesser ratio by Stages 3 and 4. In irregular undulation 89.1% of the time corresponded to Stage 2. (2) One sleep cycle was composed of the three sleep states which were accompanied with variation patterns, long undulation, irregular undulation and slight fluctuation. The sequence of the appearance of the former two patterns in one sleep cycle was classified into four types. About half of the sleep cycles in all records exhibited Type 1; the pattern started with long undulation, after one or several long undulations followed by irregular undulation and proceeded to slight fluctuation. The average number of long indulation in one sleep cycle was 1.58. (3) On all records, the highest long undulations appeared in the first cycle of all night sleep, in both frontal and central areas. In the occipital area, some of the highest crests appeared in the second cycle. When the highest of long undulations appeared, the height tended to decrease prior to wakening. The crest line of long undulation in frontal and central areas crossed in the latter period of all night sleep, in five controls. The mean voltage of long undulation in frontal, central and occipital areas was 52.4, 42.5 and 23.5 microvolts, respectively. The underlying physiological mechanism of delta waves in human sleep EEG and possible brain structures essential for long undulation and irregular undulation were discussed from both the clinical and experimental aspects.