EEG: brainwave generation, questions

Alan J. Robinson robin073 at maroon.tc.umn.edu
Fri Feb 2 18:24:30 EST 1996


On 30 Jan 1996 02:12:22 -0500, 
Hypnotics  <hypnotics at aol.com > wrote:

>What are the most recent theories regarding the generation of brainwaves.
>I understand that theories have been put forward regarding certain
>thalamic nuclei, which contain certain neurons firing at different rates. 
>These neurons project to the cortex and summation of these impulses are
>recorded as brainwaves.
>But is anymore known in this area?  It all seems rather vague....
>
>Also, it seems accepted that brainwaves can be broken down into their
>component sine waves by fourier transform, but what evidence is there that
>brainwaves ARE sinusoidal?  What evidence shows that brainwaves cannot
>REALLY be sawtooth in some instances, square in others etc.  Are we
>creating an artificial construct?
>

Grant:

Brainwaves tend to be a mix of different frequencies, with the 
frequency content varying quite markedly in different brain states 
such as the different stages of sleep.

How the brain generates these waves and what purpose they serve is 
still a mystery, like many aspects of brain functioning.  (These waves 
have been known since the early part of the 20th century, when the EEG 
was first developed.)

I believe that when Sir John Eccles was at Oxford he observed the 
related phenomenon of sychronization of neural firing between 
different parts of the cortex.  After something like 40ms 
following presentation of a visual stimulus, neurons which are 
quite far apart would suddenly become synchronized.  This seemed 
impossible to Eccles, based on what was then known about the 
architecture of the brain and how neurons worked.  He mentioned this 
to his physicist friends, and started a competition among scientists 
which continues to this day to see who can come up with the most 
bizzare theory of how neurons work.  <g>

AJR




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