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Kat Nagel wrote:
>
> Brad DeMond asked:
> >>Can anyone tell me what alpha burst
> >>activity is? It's clearly brainwave activity, but if it indicates
> >>wakefulness, then what would indicate drowsiness? Is there such a thing a
> >>"beta" activity?
> >>
>
> Yes, there is beta activity. There are delta and theta activities, too,
> and might be even more (it's been a while since I last looked at a
> neurology text.)
>
> >From memory:
> Alpha waves, beta waves, delta waves, and theta waves are all indications
> of specific types of brain activity. They are measured using different
> channels of an EEG apparatus. Alpha activity, if I remember correctly, is
> associated with waking-state thought processes and with response to direct
> sensory stimulation (loud sounds, bright flashing lights, a fast right to
> the jaw). The other wave channels respond to 'deeper' brain activity:
> control of automatic body functions, meditation states, sleep, etc. I
> don't remember which is which.
>
These aren't recorded on different channels of an EEG machine, they are
different brain states which may (or may not) be seen on different channels,
depending on where the electrodes those channels are monitoring are placed
and depending on the state of arousal of the subject.
In general, delta waves indicate deep sleep or a severe neurological state
such as a coma.
Theta isn't seen much in humans, but is very characteristic of the hippocampus
of carnivores during attentive states. Theta is occasionally seen in very
inattentive humans during very boring tasks.
Alpha is found most commonly over the visual cortex and tends to indicate
idling (or meditation - which might be the same thing, depending on who's
making the argument).
Beta indicates arousal and is the normal reaction to a direct sensory
stimulation such as a light flash, loud pop, etc. It's also indicative of
REM sleep. The normal waking EEG of a human is dominated by beta waves.
Dave Fields
(who spent many years doing graduate work at the UCLA Brain Research Institute,
but somehow never quite managed to finish)...
