IUBio

EEG Vigilance/Sleep

dag.stenberg at helsinki.nospam.fi dag.stenberg at helsinki.nospam.fi
Tue May 11 12:35:59 EST 1999


Heiko Tietze <> wrote:
> On 10 May 1999 12:07:19 GMT, dag.stenberg at helsinki.nospam.fi wrote:
> ->Are you sure you define vigilance correctly? 
> I didnt dinfine, maybe thats my problem - without electrophysiological
> definition of sleep (Loomis '36 5 stages, Dement und Klintmann '57 4
> stages) - what is vigilance ?  In my opinion it is the first stage of
> sleep and so it must be related to increased alpha/theta - perhaps
> with some bursts...

By vigilance one generally means the ability of anyone brain region to
respond adequately to input. Increased vigilance = wakefulness.

By the way, both Loomis' and Dement & Kleitman's classification are
obsolete. The classification of Rechtschaffen & Kales from 1968 is still
the standard for staging of human sleep, but might be ousted as a standard
any time now.

> ->What if you put your question in both English and Dutch, maybe 
> Sorry, german I m able to speak.

That also helps, I understand German better than Dutch.

> ->It would also be helpful if you explained what your background is
> ->and why you want to know.
> Im a neuropsychologist working on this issue. All I read and know is
> the difference or modifikation in the freq.domain but the question is:
> As more sleep is induced as more the eyes are closed - with closed
> eyes the brain works "synchroniced" more alpha - that mean what does
> the increased level of alpha freq. means ? sleep or closed eyes ?
> (sorry about my english)

Alpha occurs regularly in normal persons who are awake, but relaxed and
with closed eyes. It is maximal in occiptal areas. Alpha is more 
synchronized in people with low visual imagining tendency. Alpha
disappears on going to sleep.
  Frequency is one thing, synchronization another. Alpha frequency has
been related both to the IQ of the individual, to body temperature etc.
  Alpha is the result of a certain pattern of thalamocortical circuit
function. The synchrony of large groups of thalamocortical projection
neurons create higher amplitude. The thalamic neurons act in smaller 
functional groups when fully alert, actually seeing, or dropping off to
sleep - hence the lower amplitude.
  As far as I understand more sleep is NOT induced as the eyes are
closed more!
  Are we discussing the same thing at all?

Dag Stenberg




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