- In primates, yawning may be contagious
or a signal meant to synchronize sleep times.
Yawning is associated with sleepiness and
appears to occur in all mammals
and in some birds, and may even occur in
reptiles. Yawns are involuntary openings of the
mouth, inspiration of a breath, closing of the
eyes, and stretching of torso and limbs. Like
REM sleep, yawning is associated with
cholinergic excitation and dopaminergic
inhibition. Oxytocin
and testosterone infusions can induce yawns as
well. Interestingly, when oxytocin is injected
into paraventricular
nucleus or the hippocampus, it induces
both\yawning and penile erections. Yawning
occurs in the fetus and throughout the life
span.
-
- In humans, at least one form of yawning is
contagious-just the sight of another person
yawning can trigger a yawn, suggesting a social
function for yawning. When yawning functions as
a signal (as in the case of contagious yawning),
then t may acquire costly traits (placing the
yawner in a vulnerable position, etc.). In that
case, receivers will tend to use the signal to
infer the current status of the -sender.
According to costly signaling theory, the yawn
would then convey a message that implies that
the sender is currently handicapped ("I am not
fully aroused and my attentional skills are
flagging, etc., and therefore I am vulnerable").
But it is far from clear whether such an
analysis helps us to understand the functions,
if any, of contagious yawning. A far more likely
explanation is that the contagious yawn serves
to synchronize sleep behaviors of a group of
primates.
-
- Comparative data on other forms of
(noncontagious) yawning in relation to sleep
variables are lacking and thus not much can be
said about their functions and potential
relation to sleep. Nevertheless, the yawn's
wide taxonomic distribution in the animal
kingdom suggests an ancient lineage as well
as an important functional relationship with
sleep states. It would be interesting to know
whether manipulations of yawning (i.e.,
inhibiting or enhancing rates of yawning) have
systematic effects on either REM or NREM (or
both). It would further be interesting to know
whether yawning occurs in species with little or
no REM.
-
-
- Walusinski O,
Deputte BL. Le bâillement:
phylogenèse, éthologie,
nosogénie. Rev Neurol (Paris).
2004;160(11):1011-1021.
-
- Walusinski
O, Kurjak A, Andonotopo W, Azumendi G. Fetal
yawning assessed by 3D and 4D sonography. The
Ultrasound Rev Obs Gyncecol.
2005;5(3):210-217.
-
- Walusinski O, Quoirin
E, Neau JP. Parakinesia brachialis oscitans.
Rev Neurol (Paris). 2005;161(2):193-200.
-
- Walusinski
O. Yawning: Unsuspected avenue for a better
understanding of arousal and interoception. Med
Hypotheses. 2006;67(1):6-1
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