The functional relationship between yawning and vigilance

• Published in: Behavioural brain research Vol. 179; no. 1; pp. 159 - 166
• Main Authors: Guggisberg, Adrian G., Mathis, Johannes, Herrmann, Uli S., Hess, Christian W.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 16.04.2007; Elsevier Science
• Subjects: Adolescent; Adult; Arousal; Arousal - physiology; Behavioral psychophysiology; Behaviour; Biological and medical sciences; Communication; Electroencephalography; Female; Fundamental and applied biological sciences. Psychology; Heart Rate - physiology; Humans; Maintenance of wakefulness test; Male; Middle Aged; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Sleep - physiology; Stereotyped Behavior - physiology; Vigilance; Wakefulness - physiology; Yawning; Yawning - physiology; Vigilance; Yawning; Behaviour; Maintenance of wakefulness test; Arousal; Communication; Wakefulness; Sleep wake cycle; Behavior
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2007.01.027

Although yawning is a ubiquitous and phylogenetically old phenomenon, its origin and purpose remain unclear. The study aimed at testing the widely held hypothesis that yawning is triggered by drowsiness and brings about a reversal or suspension of the process of falling asleep. Subjects complaining of excessive sleepiness were spontaneously yawning while trying to stay awake in a quiet and darkened room. Changes in their electroencephalogram (EEG) and heart rate variability (HRV) associated with yawning were compared to changes associated with isolated voluntary body movements. Special care was taken to remove eye blink- and movement-artefacts from the recorded signals. Yawns were preceded and followed by a significantly greater delta activity in EEG than movements ( p ≤ 0.008). After yawning, alpha rhythms were attenuated, decelerated, and shifted towards central brain regions ( p ≤ 0.01), whereas after movements, they were attenuated and accelerated ( p < 0.02). A significant transient increase of HRV occurred after the onset of yawning and movements, which was followed by a significant slow decrease peaking 17 s after onset ( p < 0.0001). No difference in HRV changes was found between yawns and movements. Yawning occurred during periods with increased drowsiness and sleep pressure, but was not followed by a measurable increase of the arousal level of the brain. It was neither triggered nor followed by a specific autonomic activation. Our results therefore confirm that yawns occur due to sleepiness, but do not provide evidence for an arousing effect of yawning.