Spectral analysis of the first-night effect on the sleep-onset period

Abstract

The first-night effect (FNE) refers to the disruption of the sleep structure, which is recognized particularly on the first night of sleep in the laboratory. Difficulty in falling asleep is the most frequently reported characteristic of the FNE. We examined the FNE on the sleep-onset period (SOP) quantitatively to investigate how the wake- and the sleep-promoting systems were related to the occurrence of the FNE. Eight healthy student volunteers participated in the study. Polysomnogram recording was made for three consecutive nights. Power spectra of electroencephalogram (EEG) activities were computed by using a Fast Fourier Transform during waking and the SOP. The data obtained was divided into seven bands and the mean amplitudes in each band were calculated. On the first night, EEG amplitudes in the alpha and gamma bands were higher during waking and the SOP compared with the second and the third nights. In contrast, theta and sigma amplitudes were lower on the first night. It was suggested that the wake-promoting system was excited and the smooth activation of the sleep-promoting system was inhibited during the SOP on the first night. This phenomenon might contribute to the cause of the sleep onset difficulty, which occurs as the FNE.