Related Experiment Videos
Circadian rhythms in human performance and mood under constant conditions
T H Monk1, D J Buysse, C F Reynolds
1Department of Psychiatry, University of Pittsburgh School of Medicine, USA.
Journal of Sleep Research
|March 1, 1997
Summary
Circadian performance rhythms align with body temperature, cortisol, and melatonin levels. Subjective alertness also correlates with performance, but doesn't directly mediate these rhythms.
Area of Science:
- Chronobiology
- Human Physiology
- Cognitive Performance
Background:
- Circadian rhythms influence physiological and cognitive functions.
- Understanding the interplay between internal biological rhythms and performance is crucial for optimizing human functioning.
- Previous research has indicated correlations between performance and various biological markers, but the precise relationships under controlled conditions require further investigation.
Purpose of the Study:
- To investigate the relationship between circadian performance rhythms and rhythms in rectal temperature, plasma cortisol, plasma melatonin, and subjective alertness and well-being.
- To determine the extent to which performance rhythms vary across different tasks when the sleep/wake cycle is suspended.
- To examine the correlations between performance and physiological markers (temperature, cortisol, melatonin) and subjective states (alertness, well-being).
Main Methods:
- Seventeen healthy young adults underwent 36 hours of 'unmasking' conditions to disrupt normal circadian cues.
- Rectal temperature was measured every minute; plasma cortisol and melatonin every 20 minutes.
- Hourly subjective ratings and performance on serial search, verbal reasoning, manual dexterity, and visual vigilance tasks were recorded.
Main Results:
- Performance on most tasks showed significant time-of-day variation, with troughs near the lowest rectal temperature.
- Performance rhythms did not reliably differ with working memory load.
- Positive correlations were found between good performance and higher temperatures/alertness; negative correlations with higher cortisol/melatonin levels.
Conclusions:
- Circadian performance rhythms exhibit minimal between-task heterogeneity when the sleep/wake cycle is suspended.
- Body temperature (positively), cortisol, and melatonin (negatively) serve as effective circadian correlates of performance.
- Subjective alertness correlates with performance rhythms similarly to body temperature, suggesting it does not directly mediate performance rhythms.