The following is part of a list server discussion on "good" and "bad" brain rhythms and detecting them, especially Gamma. It also mentions clairvoyance and gamma and published research on the topic.
Gottfried,
Welcome to the list!
Gamma is generally considered "40 Hz", and its practical measurement is done on a band of 38-42 or even 35-45, to get faster filter response.
Thatcher calls 25.5 - 30.5 "gamma", and his "beta3" is 18-25.5. So there is some precedent for calling anything above 25 Hz "gamma".
In order to distinguish hibeta from gamma, you need to look beyond the amplitude of a frequency band. They differ in their frequency distribution (hibeta is broader), waxing and waning (hibeta has longer spindles, gamma is typically short bursts), and coherence (hibeta has low coherence, gamma typically has higher coherence).
To train them separately, you can use techniques such as multiple bands for enhance/inhibit, using visual inspection to tell them apart, using coherence or sum-channel approaches to separate them, etc.
And yes it it likely that different people "use" the EEG properties differently. Advanced meditators are doing perceptual and cognitive "binding" and other mental tasks, while people who are nervous or anxious are just "buzzing". The analogy between speeders and race car drivers is very appropriate.
Also, proper gamma is something that is modulated, and purposeful, and has a characteristic waxing and waning, as do all healthy brain rhythms. Any rhythm, including high beta, if it is just droning on and on under no particular regulation, can be a problem.
Best Regards,
Tom
Houman and Gottfried,
Yes, the apparent contradiction appears for all bands
including theta, alpha, beta, etc. All components are "good"
in some contexts, and "not so good" in others.
The issue is one of flexibility and appropriateness, not just whether the amplitude is there. For example, theta while doing creative activities works, while excess and uncontrolled theta in math class can be a problem. Similarly, waxing and waning occipital eyes-closed alpha indicates a healthy brain, while
sustained, diffuse alpha can indicate chronic anxiety. Just two examples.
BrainMaster uses digital filters in addition to FFT's, as each method has its value. All transform-based methods including Fourier, Gabor, and Wavelet, have the same window-related deficiencies. All they change is the "kernel" of the integration, which is an incremental benefit.
Digital filtering provides very fast response, and is absent of windowing errors. That is why we use it for most training. To detect synchronous gamma, using sum-channel training is very powerful as one approach, as you can easily detect single bursts of gamma, even very small ones. There is an example of this in my report:
http://www.brainm.com/software/2.5/2chanbrainscapes.pdf
On the bottom of page 3, for example, there is a single nice gamma burst detected in F3 and F4. With this type of setup, you could train the occurrence of these bursts, which are associated with sensory and perceptual "binding" and higher functions. This method will reject high beta waves that are asynchronous, and will train the synchronous gamma. This is a very powerful technique!
Also, if you want to see a report from 1987 reporting gamma bursts in a documented clairvoyant, see:
http://www.brainmaster.com/tfc/index_files/Publications/535-034%20Psi.pdf
This was one of the first reports of gamma in a "superconscious" person, and includes extensive EEG analysis. If you were to train these rhythms properly, you could very likely enhance such abilities, and that is a scientific fact.
The mathematical and technical reasoning behind the measurements used in this paper is documented in:
http://www.brainmaster.com/tfc/index_files/Publications/535-033%20transient-event%20model.pdf
Also, a recent report, with the data shown, is at:
http://www.brainmaster.com/tfc/index_files/Publications/psipaper.pdf
You could also use a "comb filter" approach to detect bursts, but you need to know the bursting rate. Gamma sometimes appears in bursts
of 6-7 per second, actually "riding" on a theta wave! So there is a connection between theta and gamma. And this is for "one kind" of theta. There are at least 3 types of theta, being "regular" theta, "slow alpha", and also "fast slow cortical potentials." Any of these can be in the range of 4-8 Hz, so there is not one "theta" only.
The situation is complex, and frequency and amplitude alone do not tell the whole story. Just another reason why connectivity is such an important aspect, as well.
Best Regards,
Tom
----- Original Message -----
From: "Houman Owhadi" <owhadi@caltech.edu>
To: <brainm@yahoogroups.com>
Sent: Thursday, September 27, 2007 10:51 AM
Subject: [brainm] Re:meditation eeg and neurofeedback
Hi Gottfried,
Yes the frequency range 25-42Hz is not specific enough, it would be interesting to know what happens when you uptrain 38-42Hz. (or even
80-120 HZ). From a different point of view I am currently reading a lot of material on Neurofeedback and some statements appear to contradict
each other (for instance "high Theta waves are linked to ADHD", "Theta waves promote healing and creativity.", "you should downtrain Theta", "you should not downtrain theta because it is a natural memory scanning mechanism")
This usually happens when the parameters (amplitudes/energies in each frequency) are not sufficient to characterize the system (the state of the patient) and depending on the values of this unknown parameters, uptraining or downtraining the known ones may promote attention or anxiety. that would explain why the field is so empirical and mainly based on clinical experience when one goes beyond some rigorous well established papers such as Sterman and Wyrwicka, 1967 and Wyrwicka and Sterman, 1968 ... in the end our understanding of the brain is still in its infancy...
Another point I don't understand why people are still using a Fourier Transform and not a Gabor transform (or a even a digital wavelet) which are more suited for time windowed frequency analysis.
Regards,
Houman
--- In brainm@yahoogroups.com, gArens <mailinglist@...> wrote:
>
>
> Hi all,
>
> I am new to that list since a few weeks ( and after returning from a
> journey I have had time now to go through the articeles.)
> Thank you Houman for posting the links concerning EEG and meditation.
>
> I have got 2 or 3 remarks or questions to article:
> http://www.pnas.org/cgi/reprint/101/46/16369
> "Long term meditators ..."
>
> 1st :
> The gamma band was defined in that article as to be in the range
from 25-42 Hz.
> However, frequency bands are not standardized
> (see e.g.: http://www.appliedneuroscience.nl/file.php?fId=149
> (Power Point) page: 4, 47, 48 and 57) but according to my knowledge
> the gamma band usually is defined to be in the range of 38-42 Hz and
> not starting at 25 Hz. The frequency band 25-38 Hz is called high Beta.
>
> 2nd :
> The HiBeta Band "normally" is trained down, since a to high amplitude
> in HiBeta is mentioned to be related to over excitation or stress. If
> the article found an increase in Gamma (25-42 Hz) amplitude during
> meditation of long term meditators and meditation is a state or
> condition being more calm and relaxed
>
> ins't that a kind of a contradiction ?
>
> 3rd :
> or is it that a higher HiBeta/Gamma amplitude causes stress in non
> evolved/mature/sophisticated persons whereas evolved persons (still)
feel
> comfortable having higher amplitudes in HiBeta/Gamma, like ordinary
> persons tend to have stress driving a car at 100 miles per hour or
faster
> and racing car drivers still feel good at that pace ?
>
> Regards
>
> Gottfried Arens
>
> ------------------------------
> INet : http://www.soft-dynamics.de
> eMail : mailinglist@...
>
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