- -Goren;
Friedmann Yawning : an aura for an L Dopa
induced "off" in Parkinson diesease Neurology
1998;50(3):823
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- A colleague told me that he had just seen a
patient who had been bothered by yawning for the
past two years and wanted to do something about
it. It apparently was not due to any
identifiable disorder or medication. It turns
out, unbeknownst to my friend, that I had
co-authored a case report on yawning in
Parkinson's disease (PD). My report described a
man who had suffered from PD for many years and
suffered from severe clinical fluctuaations, the
so-called "on-off" problem. He told me that
about two minutes or so before his medications
"kicked in" and put him into an "on" phase he
would yawn. He otherwise didn't yawn, and he
denied sleepiness. I witnessed this once. He was
stuck in a wheelchair, unable to stand and walk;
he was stiff, slow, and pretty well frozen in
place. He then began to yawn and two minutes
later he was dyskinetic but mobile, able to
stand up and walk by himself This had not been
described in the literature before, and,
although I hadn't a clue as to what this "meant"
in the greater scheme of neurotransmitter
physiology, I was sure it meant something.
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- I later learned that yawning was a very
common reaction to one of the standard
medications used in Europe for many years to
treat PD, apomorphine, but that medication had
not yet been tested in the US. When I wrote my
article(and I must point out that that little
case report attracted more interest than any of
the useful observations or studies that I had
published) the only thing I knew about yawning
was that it was contagious and that it occurred
not only when humans are sleepy or bored, but
also when they are nervous.
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- When my friend contacted me recently about
his yawner, I did a Pubmed search and was
floored to find out how many people had written
articles about yawning. There was even an
interesting exchange between two groups of
experts on the evolution of the yawn. There were
clever studies showing that yawning was
contagious in birds, as well as primates, and
that the yawning was not simply diurnal. Sexual
behavior of male rodents from a strain with
increased yawning was reported. And there were
even articles relating yawning to diseases,
drugs and hypothetical physiological
mechanisms.
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- Is yawning so interesting or are there a lot
of researchers who are underemployed? There are
a few interesting things about yawning. The
first is that it is contagious. The second is
that yawning is widespread in the animal kingdom
and is contagious in some of them. The third is
that yawning has been identified in utero. It
seems that babies are not susceptible to
contagious yawning, at least not from their
mothers, which is, I think, a cruel trick on
mothers. But most interesting of all, at least
to a neurologist, is that some patients with a
hemiparesis from a stroke, will raise an
otherwise paralyzed arm during a yawn, as an
involuntary reflex.
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- I suspect that yawning has attracted
attention simply because it is so universal and
yet carries no identifiable benefit. In fact,
one can argue that yawning probably causes more
trouble than it solves, at least in humans.
Certainly the parent of a small, yawning child
realizes that the child needs a nap. But just as
certainly the teacher of a yawning child
realizes that the child's boredom quotient has
outweighed the interest level. Yawns are
generally not well received by the person who
may be causing the condition. On the other hand,
as a neurologist who gives fairly frequent
talks, I use the incidence of yawning and
myoclonic jerks as an inverse measure of how
good a talk I've given. No yawns, myoclonic
jerks or sleep attacks indicates a good
lecture.
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- I think of the study of yawning in non-human
species as being a continuation of "natural
phiosoph" of the 18th century, perhaps, in some
cases using 2lth century tools. When one tries
to deduce the behavioral consequences or
behavioral causes of yawning behavior in
non-primate animals, one has trod onto a
playground more philosophical than scientific,
even if one uses scientific experimental
techniques. After all, as the authors argue, it
is not at all clear that what looks like a yawn
in some species is, in fact, the same thing as a
human yawn. One paper defines a yawn as "an
extended gaping of the mouth followed by a more
rapid closure." I don't think any of us
perceives a crocodile with its mouth open, as
yawning. And just as far afield, it is unclear
if a bird displaying yawning -type movements, is
in fact yawning, and similarly for a fetal
human. And what does one make of fish, like
Siamese fighting fish, which open their mouths
and seem to yawn, although they don't have lungs
to take in air that primates do when
yawning?
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- I suspect that all normal humans yawn,
although I don't know if that's a fact. Perhaps
there are people who never yawn, no matter how
tired or bored. Would that have any meaning?
What if absence of yawning was associated with
some other unusual behavior? To be sure the
association was more than chance, we'd need to
evaluate a few patients with similar behavior.
But then, even if we found a few people with the
same sets of unusual behaviors, until we found a
genetic or physiological link, any deductions
would be speculative, not scientific.
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- Attempting to draw evolutionary advantages
to behaviors may be entertaining and challenging
but are unlikely to be good science because we
can never control all variables, and the basic
driving force of evolution is the random event.
Most results of random events are negative, but
not all. Occasional events are advantageous.
Many are likely to be neutral, and if linked to
something advantageous, live on and
prosper.
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- Yawning is more interesting than the
palmo-mental reflex or the corneo-mandibular
reflex, but what is the point of a debate on the
"meaning" of a yawn? While I like a good
argument, does anyone really care?
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