Impaired alpha rhythm in bad sleeper during nap: A high‐density electroencephalogram study

Abstract

Summary As the pace of life accelerates, poor sleep quality has become a common health problem. A wealth of sleep studies based on electroencephalogram (EEG) have found that poor sleep quality has decreased alpha rhythm during night‐time sleep. However, whether the EEG rhythm during an afternoon nap has a similar impairment has seldom been investigated. By recruiting 35 subjects for a 90‐min nap, we explored the relationship between sleep quality and the alpha rhythm, and the contribution of naps to subjective sleep experience. We found that the power of alpha rhythm in the occipital lobe negatively correlated with sleep quality. However, there was no correlation between the sleep quality at night and the sleep duration of the nap, nor the sleep quality and the proportion of each sleep period of a nap. Our present results indicated that the quality of night‐time sleep did not affect the macrostructure of the nap. Interestingly, the negative correlation between the alpha rhythm of a nap and sleep quality at night continuously existed in Wake, N1 sleep, and N2 sleep, and had the most substantial value during N2 sleep of a nap. This implies that an impaired occipital lobe alpha rhythm is a robust biomarker for poor sleep. The research is of particular significance for developing electrical neural stimulation therapy to improve sleep quality, especially for the stimuli regions for selection and the time windows for implementation.

Alpha anteriorization and theta posteriorization during deep sleep

“…Note that the absolute alpha power was measured in Zhao et al. (2022) whereas the relative frontal‐occipital power ratio was measured in our study. The two measures can be complementary in objectively quantifying the quality of sleep.…”

“…Since slow wave sleep is important for brain health (Fultz et al, 2019) and deep sleep N2 and N3 the antecedent of sleep quality, whereas alpha anteriorization is more prominent in N2 and N3, it would be expected that more pronounced alpha anteriorization can be an indicator for high-quality sleep. Note that the absolute alpha power was measured in Zhao et al (2022) whereas the relative frontal-occipital power ratio was measured in our study. The two measures can be complementary in objectively quantifying the quality of sleep.…”

“…It was recently found that the power of alpha rhythm in the occipital lobe positively correlated with sleep quality (negatively correlated with self‐rating sleep quality index) (Zhao et al., 2022). Since slow wave sleep is important for brain health (Fultz et al., 2019) and deep sleep N 2 and N 3 the antecedent of sleep quality, whereas alpha anteriorization is more prominent in N 2 and N 3, it would be expected that more pronounced alpha anteriorization can be an indicator for high‐quality sleep.…”

“…Brain states (wake, sleep, anesthesia, etc.) are profoundly associated with the spatiotemporal dynamics of brain oscillations (Adamantidis et al., 2019; Brown et al., 2010; Siclari et al., 2014; Zhao et al., 2022). The neural oscillation characteristics presented in the EEG signals are broadly associated with the depth of anesthesia (Purdon et al., 2015) and sleep stages (Berry et al., 2018; Werth et al., 1997).…”