🚀 go-pugleaf

nospam!stenberg@cc.helsinki.nospam.fi wrote:

> In bionet.neuroscience Dan & Susan Lee <danlee@gate.net> wrote:
> > It's small, but apparently some signals still get through.  As you know,
> > in REM sleep the body is essentially paralyzed, with both "input"
> > (incoming stimuli) and "output" (signals to muscles) blockaded.  I
> > believe the inhibition occurs in the thalamic sensory-relay nucluei
> > (raphe nucleus?  can't recall exactly).
>
> The inhibition converges on the anterior horn motor neurons, which are
> hyperpolarized, apparently by glycine. The origin of this projection are
> the magnocellular nuclei in the medulla oblongata. These are activated,
> during REM sleep, by descending projections from the pons, which in turn
> dervie most of their activation from the cholinergic LDT/PPT area in the
> dorsal part of the junction of mesencephalon and pons.
>   The main pathway is thus: LDT/PPT -> pontine reticular formation ->
> magnocellular nucleus of the medulla oblongata -> motoneurons.
>   The input to the LDT/PPT is less clear. A new concept is that part of
> this REMS-inducing activity may be related to impulses from the
> amygdala. The fact that cataplexy (attacks of REM sleep-like atonia) can
> be induced by emotional stimuli might be an example of amygdala
> involvement, although that is absolutely not the only input to the LDT/PPT.
>   It is clear that strong signals may override the inhibition of muscle
> tone. This is seen during physiological REM sleep as muscle twitches,
> which derive mainly from a descending, excitatory, bursting output from
> the vestibular nuclei.

Thank you for that excellent explanation.  To be honest, in my
undergrad paper I had to skim over parts of the physiological
mechanism of REM sleep simply because I could not find as
detailed a description as the one you just gave.

The activity of the amygdala, however, has influenced some of
the neural-net theories that account for dreaming, specifically in
that its activity seems to account for the strong emotional content
of many dreams.

FWIW, yet another proposal I read w/respect to the lymbic system
was that REM patterns had to include a good amount of alpha
activity before dreamers in the sleep lab reported lucidity - the
hypothesis being that the hippocampus (crucial for memory
processing) had to be involved before lucidity could occur, and
hippocampus activity was only associated with alpha or beta
waves.  ?????   I read nothing else to support this idea (or the
assertion about the hippocampus & specific brain waves), and
being only a first-year grad student in clinical psych I don't even
know yet if this hypothesis makes sense..... <g>

> > However, some signals do get through - for example a dreamer who
> > has become lucid during a dream can move his (dreamed) eyes in a
> > certain pattern, up and down 3 times, for instance, and the pattern
> > will appear on an EOG.  Likewise if a lucid dreamer clenches his
> > fists during a dream, the muscles in his forearm will show a enough
> > activity to be clearly detected on an EMG, although obviously his
> > hands won't respond completely by clenching into fists (or the
> > person would have to be considered awake!)
>
> However, to call a state REM sleep would in my opinion call for the
> presence of three criteria: muscle atonia between twitches, REMs, and
> cortical activation. In the case of the lucid dreaming you describe,
> cortical activation is evidently there. Will-activated eye movements and
> will-activated muscle contractions do not, however, fit into a REM sleep
> category. REM sleep-like, rather.
>   I understand from your comment about the voluntary muscle contractions
> that they are weak, but detectable. Are the signs of muscle atonia
> (typical to REM sleep) still clearly observable - that is, is the
> resting muscle tone clearly less than during non-REM sleep and wakefulness?

I wish I could answer these questions.  The descriptions given by thesubjects
in the sleep lab (as reported in the LaBerge papers I read) usually
involved standing in a park or on a street or in some other dreamscape and
doing the pre-arranged signal-activities while immersed in whatever dream
they were experiencing.  Your description of lucid dreaming as possibly
occuring in a REM-*like* state rather than in true REM, such that signalling
is possible, is something I had not thought of.

Might make a good thesis!  <g> (Except that I will not be concentrating on
dreaming in my graduate work...)

Dan Lee