🚀 go-pugleaf

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.

> 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?  

> the EEG showed a REM sleep pattern, ....

In humans, the EEG pattern during REM sleep is not specific for REM sleep.
Or can you name any EEG parameter which would be?

Dag Stenberg
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Dag Stenberg     MD PhD                    stenberg@cc.helsinki.fi
Institute of Biomedicine		   tel: (int.+)358-9-1918532
Department of Physiology                   fax: (int.+)358-9-1918681
P.O.Box 9        (Siltavuorenpenger 20 J)   
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