Interplay between yawning and vigilance: a review of the experimental evidence.
BACKGROUND
Yawning is a phylogenetically old behavior of ubiquitous occurrence. The origin and function of this conspicuous phenomenon have been subject to speculation for centuries. A widely held hypothesis posits that yawning increases the arousal level during sleepiness; thus, providing a homeostatic regulation of vigilance.


METHODS
This chapter reviews experimental data on the relationship between yawning and vigilance that allow testing of the components and predictions of this hypothesis.


RESULTS
Behavioral studies and electroencephalographic (EEG) recordings of brain activity before and after yawning have provided consistent evidence that yawning occurs during states of low vigilance; thus, substantiating the notion that it is provoked by sleepiness. However, studies analyzing autonomic nervous activity and EEG-based indices of vigilance in yawning subjects did not find specific autonomic activations or increased arousal levels after yawning.


CONCLUSIONS
The data therefore do not support an arousing effect of yawning or a role in regulation of vigilance or autonomic tone.
Guggisberg
Adrian G
AG
Mathis
Johannes
J
Hess
Christian W
CW
D000818:Animals; D001143:Arousal / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D002940:Circadian Rhythm; D004569:Electroencephalography / Q000379:methods; D006801:Humans; D023421:Models, Animal; D015000:Yawning / Q000502:physiology*