Awareness during drowsiness: dynamics and electrophysiological correlates.

Area of Science:

• Neuroscience
• Sleep Research
• Cognitive Psychology

Background:

• Drowsiness impairs continuous attention tasks, leading to intermittent performance.
• Previous work identified ~18-second non-responding episodes during auditory tasks, linked to specific EEG frequency changes.

Purpose of the Study:

• To examine performance patterns and concurrent electroencephalogram (EEG) spectra during a visuomotor compensatory tracking task under sleep deprivation.
• To investigate the neural markers of drowsiness and behavioral lapses in humans.

Main Methods:

• Four participants underwent 42-hour sleep deprivation, performing a compensatory tracking task in 15-20 minute bouts.
• EEG spectral analysis and autocorrelation of performance time series (target disk distance from center) were used.

Main Results:

• Periods of poor performance showed near-18-second cycles, similar to previous findings.
• These performance lapses were associated with increased EEG power, particularly in the 3-4 Hz (low theta) band.
• Unlike sleep spindles, prominent EEG amplitude changes in the low theta band marked behavioral awareness shifts.

Conclusions:

• Behavioral awareness in drowsy humans is characterized by stereotyped ~18-second cycles.
• These cycles are marked by significant EEG amplitude changes in the low theta band, not sleep spindles.
• Both EEG and behavioral changes during drowsiness exhibit consistent, stereotyped temporal patterns.