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What's a Brain Wave?

F. Frank LeFever flefever at ix.netcom.com
Mon Apr 19 19:38:49 EST 1999

Besides the "normal" occasions for increased theta or delta, they may
be asssociated with pathology--e.g. Alzheimer's (theta) and
encephalopathy (delta)--and a few other less-understood deviations from
normal function, NOT necessarily during obvious drowsiness or sleep.

I have been searching in vain for info on cellular basis for this
(increased GABA activity? or--??), and/or sources (originating in
pathological tissue itself? or from nuclei responsive to pathology
elsewhere?  cf. septal source for hippocampal theta? cf. pontine source
of thalamic theta?)

I understand that something so simple as hyperventilation can increase
theta, concurrently with diminished cognitive ability--but HOW?

F. Frank LeFever, Ph.D.
New York Neuropsychology Group

In <7fd7ie$3pl$1 at oravannahka.Helsinki.FI>
dag.stenberg at helsinki.nospam.fi writes: 
>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
>> 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?
>As others have pointed out, "brain waves" usually refer to EEG
>(eletroencephalographic activity), i.e. the summation potentials of
>large amounts of cortical neurons. The frequencies reflect synchronous
>activation of many neurons. 
>  Gamma waves have a frequency of more than 30 Hz (30 cycles/sec),
>small amplitude and are thus hard to record. They occur mainly during
>focussed attention in wakefulness.
>  Theta waves have a frequency in humans from 4 to 8 Hz, are not very
>regular, and mostly occur during drowsiness and sleep.
>  There are other "named" frequency bands: alpha from 8 to 13 Hz,
>mainly during relaxed wakefulness in the occipital regions of the
>A mental state dominated by aplha frewquency is described by some as
>"relaxed", bo others (like me) as unbearable tiredness (I like to be
>more active than that).
>  Delta from 0.5 to 4 Hz is irregular and occurs mainly during deep
>sleep. Sigma from 11 to 15 Hz occurs in 1 second bursts during sleep, 
>and can be seen most easily during light sleep, when delta is still
>too strong.
>  Beta from about 15 to 25 Hz has low amplitude, can occur at any
>but is said to reflect weakefulness simply because during active
>one does not have the other, larger waveforms. The slower a waveform
>the larger it tends to be in terms of electrical amplitude.
>  Trance states reflect a certain pattern of brain activity; EEG waves
>reflect a certain pattern of brain activity; thus: if you induce a
>certain brain activity state, you will see that type of EEG activity.
>Dag Stenberg
>Dag Stenberg     MD PhD                    stenberg at 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)   
>FIN-00014 University of Helsinki,Finland   

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