The perception of wakefulness within sleep

Area of Science:

• Neuroscience
• Sleep Medicine

Background:

• Understanding the relationship between subjective awareness of arousal and objective physiological measures of wakefulness is crucial for sleep research.
• Electroencephalography (EEG) is a primary tool for objectively defining sleep stages and wakefulness.

Purpose of the Study:

• To investigate the correlation between electroencephalographic (EEG)-defined awakenings and subjects' self-reported awareness of these events.
• To determine the proportion of self-signaled wakefulness that corresponds to objective EEG criteria.

Main Methods:

• 40 male subjects (mean age 55.3 years) participated in a laboratory sleep study.
• Subjects used a push-button to signal wakefulness while continuous EEG and electro-oculograms were recorded.
• Data from 12 non-responders were excluded from analysis.

Main Results:

• 52% of self-signaled wakefulness occurred during EEG-defined stage 0 (wakefulness).
• An additional 12% occurred in sleep stages immediately preceding stage 0.
• Of the remaining 36% not immediately preceded by stage 0, 73% showed preceding alpha activity (4-6 seconds), indicating subtle EEG changes.
• Less than 10% of signals occurred without any discernible EEG criteria.

Conclusions:

• Self-signaled arousals are strongly associated with objective EEG-defined wakefulness, often occurring within seconds to a minute of EEG changes.
• The findings support the clinical consideration of self-reported arousals as a valid indicator of sleep disturbance, especially when correlated with EEG data.