Center for Brain, Consciousness, and Cognition
EEG Markers during Sleep
Summary
In subjects who reported the experience of inner awareness during a night's sleep (witnessing sleep), theta/alpha power was significantly higher and muscle tone significantly lower during deep sleep compared to subjects who do not report this experience. REM density was also higher during the first three REM periods in the group reporting this experience.
This figure presents theta/alpha activity during sleep (6-10 Hz). The witnessing group (gold column) exhibited the highest amplitude of theta/alpha during the first three sleep cycles; the group of TM subjects not reporting this experience (middle column) had the next highest, and a non-meditating, comparison group (green column) had the lowest.
This figure presents a sample tracing during REM dreaming and Stage IV (deep) sleep in subjects reporting witnessing sleep. The top three lines are EEG recorded at left, mid line, and right central sites; the next two are left and right eye leads. The next is the muscle tone or EMG. Notice the alpha activity (smaller, faster waves) riding on top of the slower delta activity in the top two tracings. Also notice the muscle tone has dropped out (atonia) during deep sleep. Atonia during delta sleep has never been reported before in any other subject population.
Explanation
Mason and colleagues (Sleep, 1997) investigated EEG, muscle tone, and eye-movement density during a night's sleep in two groups who practiced the Transcendental Meditation technique and one group who did not. The first group comprised eleven subjects reporting the experience of higher states of consciousness during sleep for at least five years; the second comprised nine subjects not reporting this experience; and the last was a group of eleven subjects who did not practice the TM technique.
Similar amounts of delta EEG were seen in all three groups. Delta EEG marks the restorative value of sleep, and suggests that all subjects slept soundly. The group reporting this experience had significantly higher theta/alpha activity and decreased muscle tone than the other two groups. Atonia during delta sleep has never been reported before in any other subject population. Ongoing research is investigating this phenomenon.
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