One should point out that theta waves (a rather slow range of
frequencies) occur in drowsiness and many conditions of cerebral
impairment, but gamma waves (a range of rather high frequencies) are
associated with the opposite--in sleep, they might be associated with
REM (dreaming) activity.
I believe focal 40Hz (in the gamma range) is thought by some to
represent activity involving some salient event (Sheer's emphasis), or
(more than one focus?) "binding together" different aspects of an event
or activity (e.g. Llinas, others).
There have been various strategies for "driving" activity at designated
frequencies (of dubious validity, I believe), as well as biofeedack
procedures to selectively enhance selected frequencies; claimed
outcomes are controversial, but cannot be rejected out of hand.
F. Frank LeFever, Ph.D.
New York Neuropsychology Group
In <37110eb1.33771056 at news.ox.ac.uk> james.teo at chch.ox.ac.uk (Grushnik)
>>On Sun, 11 Apr 1999 21:03:17 +0200, Wolfgang Schwarz
><wschwarz at zedat.fu-berlin.de> wrote:
>>There are gadgets that claim to cause "Brainwave synchronisation"
>>(e.g. the once famous "Brain Machine" or even the sample editor "Cool
>>Edit"). That should lead to trance states or something like that
>>(never works in my case though). Is that just nonsense then, or what
>>are these gamma- and thetawaves they allegedly induce?
>>"Gamma and theta waves" describe states which are easily recognisable
>by their waveform on their EEG. These states are occur in sleep.
>I've never heard of those brain synchronisation things.