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Re: Evolution of sleep
On Thu, 17 Mar 2005, Jura wrote:
> --- K and T Dykes <firstname.lastname@example.org> wrote:
> <Sleep per se is common to all... vertebrates?>>
> > This must be another interesting question, because I
> > don't know the answer
> > either. Happily, there's a good chance somebody
> > else will be able to
> > enlighten us both. That's the great thing about
> > ignorance. It leaves
> > plenty of room for learning new stuff.
> > Cheers
> > Trevor
> I'm not sure how far back sleep goes, but I know that
> insects get the "honour" of being included in this
> camp. Though the physiological processes that occur in
> vertebrate sleep, are completely different with
> insects (since they have a completely different
> physiology, I'm hardly surprised). As such, insect
> sleep usually gets labeled as: torpor.
> Nonetheless, insects demonstrate the same lack of
> mobility and decreased response to stimuli, that is
> seen in vertebrates when they sleep (i.e. they "shut
> down" just like the rest of us do).
Insect "sleep" per se appears to be a recent study subject, tho circadian
rhythm study goes back a ways.
J Appl Physiol 94: 1660-1672, 2003; doi:10.1152/japplphysiol.00904.2002
Vol. 94, Issue 4, 1660-1672, April 2003
Genetic Models in Applied Physiology
Invited Review: Sleeping flies don't lie: the use of Drosophila
melanogaster to study sleep and circadian rhythms
For sleep, the use of the fly as a model is relatively new, that is, only
within the past 2 yr.
Part II: Getting to Sleep
Do flies sleep? ... To be considered sleeplike, an inactive state should
have the following features: 1) consolidated circadian periods of
immobility, 2) a species-specific posture and/or resting place, 3) an
increased arousal threshold (although the state can be reversed by
intense stimulation), and 4) a homeostatic regulatory mechanism. We found
that, according to these criteria, rest in Drosophila is a sleeplike
state. Rest in Drosophila shares with sleep the intriguing features of
prolonged immobility, lack of sensory responses, and homeostatic rebound
in response to rest deprivation, in addition to the well-known circadian
regulatory influences on activity. These flies also show conservation of
behavioral changes in response to caffeine and to an adenosine agonist
that produces sleep in mammals. We concluded that rest in these simple
animals may be considered a primordial form of the sleep state. A second
independent study reported nearly identical behavioral and
pharmacological findings and also showed that genes upregulated in
response to rest deprivation were conserved between flies and mammals.
Neuron. 2000 Jan;25(1):129-38.
Rest in Drosophila is a sleep-like state.
To facilitate the genetic study of sleep, we documented that rest
behavior in Drosophila melanogaster is a sleep-like state. The animals
choose a preferred location, become immobile for periods of up to 157 min
at a particular time in the circadian day, and are relatively
unresponsive to sensory stimuli.
Hendricks group first described Drosophila sleep in a paper published
last year in the journal Neuron. Rest in flies shares numerous
similarities with human sleep, including prolonged immobility, decreased
sensory responsiveness and a need to compensate after sleep deprivation.
Fruit flies spend about six to 10 hours a day resting, mostly at night.
"The sleeping flies lie prone in a quiet corner, unresponsive to stimuli,
for bouts averaging about 45 minutes but sometimes lasting up to
two-and-a-half hours," Hendricks said. "These sessions are interspersed
with very brief, one- to two-minute interruptions, during which they eat
and groom and then settle back down."
And see also
(how do I work dinosaurs into this?...)
> Now, do insects dream? That's what I'd like to find
Advances in - oh heck, what's that brain scanning thingie, MRI? -
might make that something that could be looked at.
> Aside from that, I'm left wondering if sleep is a
> common trait seen in all creatures that exhibit an
> ability to think (i.e. neurons capable of associating
> with each other). There was a recent article in Time
> magazine that dealt with sleep. The latest research on
> it would seem to confirm that it is a behaviour
> devoted, almost entirely, to the brain. As such, I'm
> wondering if sleep is a requirement for proper
> functioning of the associative neurons themselves. It
> would help explain why sleep is so prevalent across
> classes, and why the best some critters can do, is
> only turn off half of their brains at a time.
Some sort of circadian rhythm can be found even in one celled