Topographical Characteristics and Principal Component Structure of the Hypnagogic EEG

Abstract

The purpose of the present study was to identify the dominant topographic components of electroencephalographs (EEG) and their behavior during the waking-sleeping transition period. Somnography of nocturnal sleep was recorded on 10 male subjects. Each recording, from "lights-off" to 5 minutes after the appearance of the first sleep spindle, was analyzed. The typical EEG patterns during hypnagogic period were classified into nine EEG stages. Topographic maps demonstrated that the dominant areas of alpha-band activity moved from the posterior areas to anterior areas along the midline of the scalp. In delta-, theta-, and sigma-band activities, the differences of EEG amplitude between the focus areas (the dominant areas) and the surrounding areas increased as a function of EEG stage. To identify the dominant topographic components, a principal component analysis was carried out on a 12-channel EEG data set for each of six frequency bands. The dominant areas of alpha 2- (9.6-11.4 Hz) and alpha 3- (11.6-13.4 Hz) band activities moved from the posterior to anterior areas, respectively. The distribution of alpha 2-band activity on the scalp clearly changed just after EEG stage 3 (alpha intermittent, < 50%). On the other hand, alpha 3-band activity became dominant in anterior areas after the appearance of vertex sharp-wave bursts (EEG stage 7). For the sigma band, the amplitude of extensive areas from the frontal pole to the parietal showed a rapid rise after the onset of stage 7 (the appearance of vertex sharp-wave bursts). Based on the results, sleep onset process probably started before the onset of sleep stage 1 in standard criteria. On the other hand, the basic sleep process may start before the onset of sleep stage 2 or the manually scored spindles.

Dissociation, Resting EEG, and Subjective Sleep Experiences in Undergraduates

“…For example, since the pioneering study of Dement and Kleitman (1957), it has been known that during the transition from alert wakefulness to sleep onset (i.e., the hypnagogic state), ␣ power decreases and and ␦ power increase. These findings have been replicated in a more recent study (Tanaka et al, 1997). In line with previous findings, Cajochen et al (in Klimesch, 1999) have shown that administration of melatonin, which regulates waking and sleeping and increases sleepiness, leads to an increase in the band and a decrease in the ␣ band.…”

EEG Vigilance Regulation Patterns and Their Discriminative Power to Separate Patients with Major Depression from Healthy Controls

“…VIGALL takes into account the vigilance stages as described by authors such as Bente [18], Roth [19] and Loomis et al [20] and more recently by others [21,22,23,24,25]. In short, vigilance stages range from stage 0 (corresponding to high alertness) to stages A1, A2 and A3 (corresponding to relaxed wakefulness) and further to stages B1 and B2/3 (corresponding to increasing drowsiness) and finally to stage C (sleep onset).…”

Power and coherent oscillations distinguish REM sleep, stage 1 and wakefulness

“…Many efforts have been directed toward differentiating stage 1 from wakefulness and stage 2 focused on the process of falling asleep, and although the precise moment of sleep onset is still a matter of debate, detailed studies have been carried out to determine the precise entrance into sleep considering behavioral, physiological and subjective changes (Ogilvie et al, 1991;Hasan and Broughton, 1994;Wright et al, 1995;Tanaka et al, 1997). In contrast, little is known about differences in EEG activity between stage 1 and REM sleep, except for a couple of studies focused on alpha activity only (Armitage, 1995;Cantero et al, 1999).…”