Fundamental Brain Rhythms?

[Guest guest]

Several alternative health groups, inlcuding the Teslar watch manufacturers,

make a great deal of the belief that the alpha rhythm of the brain (8-13 Hz)

is allegedly entrained to the Schumann waves about the Earth, which appear to

have much the same frequency. It is hypothesized that, since life evolved

on this planet, the most fundamental rhythm which should have developed in

the brain is that around 7.83Hz.

For a start, we don't even know if these earthly waves have always displayed

the same characteristics and frequency, but let us put aside that concern for

a moment and focus on the brain waves themselves.

One major problem with this hypothesis is the fact that everyone's dominant

alpha rhythm is different and different areas of the brain exhibit different

alpha frequencies, as shown by some of the following studies. In addition,

since we all sleep, we might also hypothesize that the most natural basic

brain rhythm should be one of the commonly occurring sleep rhythms such as

delta (0.5 - 4Hz). However, this rhythm also changes in everyone and is

generated differently by different parts of the brain. The same refers to

other rhythms, like the beta rhythm (13-30Hz), which is produced while we are

mentally alert.

Who is to state that any given single electrical state of the brain is more

or less fundamental than any other? There simply is far too much variation,

too much individuality and too many exceptions to allow us to make any

dogmatic statements about wave entrainment, human behaviour, the relationship

between tiny external fields and equally tiny, always varying brain rhythms.

The following very small selection of relevant studies on brain electrical

activity serves to stress these points.

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Brain Res 1992 Jun 5;582(1):159-62

Functional correlates of a three-component spatial model of the alpha rhythm.

Gratton G, Villa AE, Fabiani M, Colombis G, Palin E, Bolcioni G, Fiori MG.

Dept of Clinical Neurophysiology, FIDIA Research Labs, Abano Terme, Italy.

We applied a three-component (temporal, occipital and parietal) spatial model

to EEG data obtained from 46 young and 11 elderly subjects. With closed eyes

the mean alpha frequency was 9.51 Hz for the temporal, 9.88 Hz for the

occipital and 10.14 Hz for the parietal component. The power of the occipital

component was larger than that of the others. With open eyes it was reduced

to the same level as the temporal and parietal components. The power of the

occipital component decreased significantly with age.

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Electroencephalogr Clin Neurophysiol 1995 May;94(5):305-12

Diurnal variations of EEG power in healthy adults.

Cacot P, Tesolin B, Sebban C.

Unite d'Explorations Fonctionnelles, Hopital Foix, Ivry sur Seine,

France.

EEG power variations were evaluated in 9 healthy young adults from 8.45 a.m.

to 9 p.m. and at 7 a.m. the next day. EEG signals were obtained from 16

electrodes in closed eyes and open eyes situations. Diurnal power variations

were calculated for each frequency component, according to the recording

situation (RS) and to the scalp site.

Regarding values in the early morning on the first day, the power of almost

all the frequency components showed an important diurnal increase. It came

back close to initial values at 7 a.m. on the second day, which is in

agreement with the existence of EEG circadian variations. Diurnal evolutions

were dependent on the frequency components: the higher the frequency, the

later was its diurnal maximum. For many frequency components, the diurnal

variation was dependent on RS and the scalp topography. All these

characteristics could be used to split the classical EEG bands, especially

the delta and alpha bands and be useful for physiological and pharmacological

research.

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Neuropsychobiology 1999;39(2):110-6

Spectral structure and brain mapping of human alpha activities in different

arousal states.

Cantero JL, Atienza M, Gomez C, Salas RM.

Laboratorio de Sueno, Area de Psicofisiologia Cognitiva, Sevilla, Espana.

In a study with 10 young, healthy subjects, alpha activities were studied in

three different arousal states: eyes closed in relaxed wakefulness (EC),

drowsiness (DR), and REM sleep. The alpha band was divided into three

subdivisions (slow, middle, and fast) which were analyzed separately for each

state.

The results showed a different spectral composition of alpha band according

to the physiological state of the subject. Slow alpha seemed to be

independent of the arousal state, whereas middle alpha showed a difference

between REM and the other states. The fast-alpha subdivision appears mainly

as a waking EEG component because of the increased power displayed only in

wakefulness and lower and highly stable values for DR and REM. Scalp

distribution of alpha activity was slightly different in each state: from

occipital to central regions in EC, this topography was extended to

fronto-polar areas in DR, with a contribution from occipital to frontal

regions in REM sleep.

These results provide evidence for an alpha power modulation and a different

scalp distribution according to the cerebral arousal state.

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Clin Neurophysiol 2000 May;111(5):924-8

Asymmetric interhemispheric delta waves during all-night sleep in humans.

Sekimoto M, Kato M, Kajimura N, Watanabe T, Takahashi K, Okuma T.

National Center Hospital for Mental, Nervous and Muscular Disorders, National

Center of Neurology and Psychiatry, Tokyo, Japan.

OBJECTIVE: In order to better understand the asymmetry of brain function

during sleep, period-amplitude analysis of delta EEG activity was performed

on polysomnograms (PSGs) in normal humans. Twenty healthy, right-handed male

volunteers aged 22-35 years (mean age 27.2 years) served as subjects in this

study.

METHODS: EEGs were recorded from disc electrodes placed at bilateral frontal,

central, parietal, occipital, anterotemporal and posterotemporal (10-20

electrode system) sites using A1+A2 for reference. Period-amplitude analysis

was performed by the zero-crossing method using the Medilog Sleep Analyzing

Computer.

RESULTS: Delta counts in the right frontal and central regions during

all-night sleep were significantly greater than in those of the left; total

delta counts of the right frontal region were greater than those of the left

in 18 of the 20 subjects. There were no significant differences in delta

counts between the left and right hemispheres in parietal, occipital,

anterotemporal, and postero-temporal regions.

CONCLUSIONS: These results suggest distinct laterality in the number of delta

waves in the frontal and central regions, reflecting functional asymmetry of

the brain during sleep.

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Dr Mel C Siff

Denver, USA

http://groups.yahoo.com/group/Supertraining/