Brain Activity types
Alpha
is the frequency range from
8
Hz
to 13.9 Hz Relaxation,
superlearning, relaxed focus, light trance, increased serontonin
production. Pre-sleep, pre-waking drowsiness, meditation, beginning of
access to unconscious mind
Beta
is the frequency range from
14 Hz to
about 30 Hz Concentration,
arousal, alertness, cognition. Higher levels associated with anxiety,
unease, feelings of separation, fight or flight.
Delta is the frequency range
.1 to 3.9 Hz
Dreamless sleep Human growth hormone released. Deep, trance-like,
non-physical state, loss of body awareness. Access to unconscious and
“collective unconscious” mind.
Theta is the frequency range
from
4 Hz to 7.9
Hz Dreaming sleep (REM
sleep) Increased production of catecholamines (vital for learning and
memory), increased creativity. Integrative, emotional experiences,
potential change in behavior, increased retention of learned material.
Hypnagogic imagery, trance, deep meditation, access to unconscious mind.
Gamma
is the frequency range approximately
26–100 Hz
The EEG
typically described in terms of (1) rhythmic activity and (2)
transients. The rhythmic activity is divided into bands by frequency. To
some degree, these frequency bands are a matter of nomenclature (i.e.,
any rhythmic activity between 8-13.9 Hz can be
described as "alpha"), but these designations arose because
rhythmic activity within a certain frequency range was noted to have a
certain distribution over the scalp or a certain biological
significance.
Most of
the cerebral signal observed in the scalp EEG comes falls in the range
of 1-20 Hz.
-
Delta is the frequency range up
to 3.9 Hz.
It is seen normally in adults in
slow wave sleep. It is also seen normally in babies.
-
Theta is the frequency range
from 4 Hz to 7.9 Hz.
Theta is seen normally in young children. It may be seen in
drowsiness or arousal in older children and adults; it can also be
seen in
meditation. Excess theta for age represents abnormal activity.
-
Alpha is the frequency range
from 8
Hz to 13.9 Hz.
This is activity in the 8-12 Hz range seen in the posterior head
regions when an adult patient is awake but relaxed. It was noted to
attenuate with eye opening or mental exertion. The posterior basic
rhythm is actually slower than 8 Hz in young children (therefore
technically in the theta range
-
Beta is the frequency range from
12 Hz to about 30 Hz.
Low amplitude beta with multiple and varying frequencies is often
associated with active, busy or anxious thinking and active
concentration. Rhythmic beta with a dominant set of frequencies is
associated with various pathologies and drug effects, especially
benzodiazepines.
-
Gamma is the frequency range
approximately 26–100 Hz.
Gamma rhythms are thought to represent binding of different
populations of neurons together into a network for the purpose of
carrying out a certain cognitive or motor function.
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