Brain Wave Frequency Ranges
An Introduction:
Brain waves are a
by-product of nerves firing and resting.
These neurons fire in differing patterns that result in constantly
varying levels of slow and fast wave activity.
One way of distinguishing these different levels is by measuring the
relative speed of each the waves. An
example of this can be found on your radio FM dial. Each radio station is
assigned a number on the dial. If viewed on an electronic oscilloscope, a
signal that was assigned 100.5 on the dial could be seen cycling 100.5
times. We use the term “hertz” or “Hz”
to count the number of cycles per second for the wave. Higher numbers suggest a faster and more intense
level of wave activity. Slower number suggests a slower level of activity. Each
wave serves particular purpose and the brain constantly changes the proportion
of each wave from moment to moment accordingly.
While the human electroencephalogram (EEG) goes well above 42 hz.,
current biofeedback equipment is unable to accurately measure above 42 hz because of the
insulation of the skin, scalp, and bone.
Here is a break down of the current way of viewing differing levels of relaxation and stages of being alert.
Delta .5-2.0 Hz |
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This frequency rage is the slowest and when dominant brings about unconsciousness and sleep states.
Theta 3-7 Hz |
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These waves are a bit faster. While more alert than delta, theta waves create consciousness that is introspective and less aware of the outside environment. When we are lost in a daydream, in prayer or meditation, these waves are likely to be dominant. Theta waves are associated with creativity, intuition, and strong negative emotions. The lower range of theta (3-5hz) can be problematic for trauma, perceptual distortions (e.g. “I never get a break."), and Attention Deficit Disorder. One goal of Neurofeedback is to reduce to the proportions of 3-5hz to improve attention and mood.
Alpha 8-12 Hz |
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Higher levels of alpha waves with eyes closed usually stimulates relaxed and pleasant emotional states. Alpha may be stimulated when praying, meditating, listening to relaxing music, or sitting on a beach. There are some exceptions to this. High levels of alpha when eyes are open may impair attention, or be associated with fear or anxiety states. Research has also shown that excessive alpha on the left side can predispose one to states of depression. Among meditators and biofeedback practitioners, deep alpha states with eyes closed help to promote emotional healing and personal integration.
Sensory Motor Rhythm(AKA “SMR”) 13-15 Hz |
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This range begins the lowest region of what is called “Beta” waves. You might want to think of SMR as being an “idle speed” that is balance of both alert and very calm. In Neurofeedback, this range is most often trained on the right side. While training in SMR people have an increased sense of body awareness and there is often a restoration of the body’s circadian rhythms.
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Beta Waves 15-45 hz |
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This larger range has frequencies that are increasingly more alert and aware of environmental demands.
· 15-18 Hz Often used as a target range for the left side. The slightly higher side helps to prevent depressive states.
· 19-21 Hz (Aura) This range often stimulates an alert and objective “witness state.”
· 24-38 Hz This range is often experienced by people as vigilance, worry, and unproductive anxiety. During biofeedback training it is often desirable to reduce the proportion of these wave frequencies.
· 38-42 Hz (Peak Performance) Curiously, while this short range is above the anxiety range, it is usually experienced as a state where one is alert, coordinated, and highly functional. Olympic performers and athletes have been known to train in this range to improve their coordination and gross motor abilities.