Brainwaves and Frequency Bands
The EEG (electroencephalograph) measures brainwaves of different frequencies within the brain. Electrodes are placed on 1020 system specific sites on the scalp to detect and record the electrical impulses within the brain. A frequency is the number of times a wave repeats itself within a second. Sometimes called Cycles per second or Hertz. If any of these frequencies are deficient or excessive our mental performance can suffer.
For example: Our brain uses 13 Hz (high alpha or low beta) for “active” intelligence. Often we find individuals who exhibit learning disabilities and attention problems having a deficiency of 13 Hz activity in certain brain regions that effects the ability easily to perform sequencing tasks and math calculations.
Amplitude represents the power of electrical impulses generated by collective neurons. Volume or intensity of brain wave activity is measured in microvolts. The raw EEG has usually been described in terms of frequency bands:
The following provides information on the Brain Wave Frequency bands
Delta (0.1 to 4) Hz
The lowest frequencies are delta. These are less than 4 Hz and occur in deep sleep and in some abnormal processes also during experiences of “empathy Delta waves are involved with our ability to integrate and let go. It reflects unconscious mind. Delta is normally the dominant rhythm in infants up to one year of age and it is present in stages 3 and 4 of sleep. It tends to be the highest in amplitude and the slowest waves. We increase Delta waves to decrease our awareness of the physical world. We also access information in our unconscious mind through Delta.
Peak performers decrease Delta waves when high focus and peak performance is required. However, most individuals diagnosed with Attention Deficit Disorder, naturally increase rather than decrease Delta activity when trying to focus. The inappropriate Delta response often severely restricts the ability to focus and maintain attention. It is as if the brain is locked into a perpetual drowsy state.
Subjective feeling states: deep, dreamless sleep, non-REM sleep, trance, unconscious.
Associated tasks & behaviours: lethargic, not moving, not attentive
Physiological correlates: not moving, low-level of arousal.
The next frequency band in the spectrum is: Theta (4-8) Hz
Theta activity has a frequency of (3.5 to 7.5) Hz and is classed as “slow” activity. It is seen in connection with creativity, intuition and daydreaming and is a repository for memories, emotions, sensations. Theta waves are strong during internal focus, meditation, prayer, and spiritual awareness. It reflects the state between wakefulness and sleep. Relates to subconscious.
It is abnormal in awake adults but is perfectly normal in children up to 13 years old. It is also present during sleep. Theta is believed to reflect activity from the limbic system and hippocampus regions.
Theta is observed in anxiety, behavioural activation and behavioural inhibition. When the theta rhythm appears to function normally it mediates and promotes adaptive, complex behaviours such as learning and memory. Under unusual emotional circumstances, such as stress or disease states, there may be an imbalance of three major transmitter systems, which results in aberrant behaviour.
Subjective feeling states: intuitive, creative, recall, fantasy, imagery, creative, dreamlike, switching thoughts, drowsy
Associated tasks & behaviours: creative, intuitive; but may also be distracted, unfocused
Physiological correlates: healing, integration of mind/body.
The next frequency band in the spectrum is: Alpha (8-12 Hz).
Alpha waves are those between (7.5 and 13)Hz. Alpha waves will peak around 10 Hz. Good healthy alpha production promotes mental resourcefulness, aids in the ability to coordinate mentally, enhances overall sense of relaxation and fatigue. In this state you can move quickly and efficiently to accomplish whatever task is at hand.
When Alpha predominates most people feel at ease and calm. Alpha appears to bridge the conscious to the subconscious.It is the major rhythm seen in normal relaxed adults – it is present during most of life especially beyond the thirteenth year when it dominates the resting.
Alpha rhythms are reported to be derived from the white matter of the brain. The white matter can be considered the part of the brain that connects all parts with each other.
It is a preferred state for the brain and occurs whenever a person is alert (it is a marker for alertness and sleep), but not actively processing information. Alpha waves are strongest over the occipital (back of the head) cortex and also over frontal cortex.
Alpha has been linked to extroversion (introverts show less), creativity (creative subjects show alpha when listening and coming to a solution for creative problems), and mental work. When your alpha is with in normal ranges we tend to experience also good moods, see the world truthfully, and have a sense of calmness. Alpha is one of the brain’s most important frequency to learn and use information taught in the classroom and on the job. You can increase alpha by closing your eyes or deep breathing or decrease alpha by thinking or calculating. Alpha-Theta training can create an increase in sensation, abstract thinking and self-control. Alpha allows us to shift easily from one task to another.
Subjective feeling states: relaxed, not agitated, but not drowsy; tranquil, conscious
Associated tasks & behaviours: meditation, no action
Physiological correlates: relaxed, healing
Sub band low alpha: (8-10)Hz: inner-awareness of self, mind/body integration, balance
Sub band high alpha: (10-12)Hz: healing, mind/body connection.
The next frequency band in the spectrum is: Beta (above 13 Hz).
Beta activity is fast activity. It reflects desynchronised active brain tissue. It is usually seen on both sides in symmetrical distribution and is most evident frontally. It may be absent or reduced in areas of cortical damage.It is generally regarded as a normal rhythm.It is the dominant rhythm in those who are alert or anxious or who have their eyes open. Beta fast is the state that most of brain is in when we have our eyes open and are listening and thinking during analytical problem solving, judgment, decision making, processing information about the world around us.
The beta band has a relatively large range, and has been divided into low, midrange and high.
Low Beta (13-15) Hz, formerly “SMR”:(Sensory Motor Rhythm)
Subjective feeling states: relaxed yet focused, integrated
Associated tasks & behaviours: low SMR can reflect “ADD”, lack of focused attention Physiological correlates: is inhibited by motion; restraining body may increase SMR
Midrange Beta (15-18) Hz
Subjective feeling states: thinking, aware of self & surroundings
Associated tasks & behaviours: mental activity
Physiological correlates: alert, active, but not agitated
High Beta (above 18 Hz):
Subjective feeling states: alertness, agitation
Associated tasks & behaviours: mental activity, e.g. math, planning, etc.
Physiological correlates: general activation of mind & body functions.
The next frequency band in the spectrum is: Gamma (above 36 Hz).
Gamma is measured between (36 – 44) Hz and is the only frequency group found in every part of the brain. When the brain needs to process simultaneously information from different areas, its hypothesized that the 40 Hz activity consolidates the required areas for simultaneous processing. A good memory is associated with well-regulated and efficient 40 Hz activity, whereas a 40 Hz deficiency creates learning disabilities.
Gamma (40 Hz):
Subjective feeling states: thinking; integrated thoughts
Associated tasks & behaviours: high-level information processing, “binding”
Physiological correlates: associated with information-rich task processing
Click on either the “brain” on the left to see lobes of the Brain.
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