entrainment

Robert Arnott R.H.Arnott at sheffield.ac.uk
Thu Oct 17 07:04:29 EST 1996


>If you prime the nervous sytem with a harmonic stimulus of
>say 4 hertz via sound, viberation, and flashing light,
>would this reduce the need for anaesthetic chemicals because
>it entrained the brain into a LOW conscious state?

Dear Ron,

I'm afraid I don't know.

A researcher who worked in our lab a couple of years ago was also
interested in measurement of human auditory evoked responses as a possible
means for assessing anaesthetic depth in clinical practice.   In his
initial experiments he blindfolded conscious subjects and administered
clicks at 1 Hz binaurally.   When I acted as one of his subjects, I found
the experience very soporific but I don't know whether this was related to
the stimulus or whether it was induced by sitting blindfolded in a nice
warm room.   I actually suspect a bit of both but I don't know whether this
was reported by any of his other subjects.

Unfortunately I am not sure that a phenomenon such as this would enable
much reduction in administration dose of anaesthetics.   When we conduct
our experiments in anaesthetised animals, delivery of a noxious stimulus
(such as pinching the foot or increasing the amplitude and duration of
electrical stimuli) causes quite marked changes in both the
electrocorticogram (ECoG) and the stimulus-evoked response.   We see a
reduction in latency and increase in amplitude of cortical mass evoked
responses and a change in ECoG from high voltage low frequency (HVLF)
activity to low voltage high frequency (LVHF) activity, both of these
changes being associated with increased arousal (Angel, 1991).   I wonder
whether the arousing effect of painful stimulation would completely
overwhelm the possible soporific effect of low frequency auditory or visual
stimulation.   Certainly it would be interesting to examine experimentally
whether delivery of low frequency stimulation has a soporific effect.

Sorry I can't be more helpful.

Robert

Reference:

Angel, A. (1991):  Adventures in Anaesthesia.   Experimental Physiology.
Vol. 76 pp. 1-38




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Robert Arnott,
Centre for Research in Anaesthetic Mechanisms,
Department of Biomedical Science,
The University of Sheffield,
SHEFFIELD.
S10 2TN
England

email   r.h.arnott at sheffield.ac.uk

Telephone +44114 276 8555 ext. 4660
Fax +44114 276 5413
URL http://www.shef.ac.uk/uni/academic/A-C/amrc/

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