Band Attributes and QEEG Metrics

Band Attributes


Delta occurs in deep sleep, during periods of empathy, when areas of the brain to ‘off line’ to take up nourishment and during complex problem solving. Increased Delta decreases our awareness of the physical world.  Information in the unconscious mind is accessed through Delta.

Delta waves are involved with the ability to integrate and ‘let go.’  Delta is a ‘healing’ band.  It appears to be associated with the Autonomic Nervous system.

An inappropriate Delta response appears to restrict the ability to focus and maintain attention. It is as if the brain is locked into a perpetual drowsy state. Parietal delta (P4) affects association and cortex/processing. A delta deficit is indicative of problems with working memory.


Theta activity is classified as “slow” activity. It is a repository for memories, emotions, and sensations.  It relates to the subconscious.  It is seen as a precursor and sequel to sleep.

Theta generally represents a more daydream like, fantasy prone state of mind that is associated with mental inefficiency. At very slow levels, theta brainwave activity is a very relaxed state, representing the twilight zone between waking and sleep. When theta is high, the brain appears to be working overtime to recruit resources.  It is theorized that this may be due to a lack of nutritive resources available. 

Increased theta and beta have been described as ‘driving with the brakes on.’  (The brain does not ‘run’ fluidly).

Excessive frontal slow wave activity can result in difficulty controlling attention, behaviour and emotions.  This presentation further correlates with difficulty with cognitive processing, concentration, memory, impulse and mood control, focus, hyperactivity, etc. 

Theta is observed in anxiety, behavioral activation and behavioral inhibition. When the theta rhythm appears to function normally it mediates and promotes adaptive, complex behaviors such as learning and memory.


When alpha is with in ‘normal’ range, one tends to experience good moods, see the world truthfully, and have a sense of calmness. Alpha supports learning and use of information taught in the classroom and on the job.

Healthy alpha production promotes mental resourcefulness, aids in the ability to coordinate mentally, enhances overall sense of relaxation and fatigue. It allows one to 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

If Alpha is blunted or absent, individuals may cite poor retention of information and/or poor short-term memory. When the Alpha blocking response (increased amplitude in the eyes closed state) is non-existent or negative then possibility of traumatic stress may be investigated.

Too much alpha suggests ‘slowing’ of the area where it is elevated.  (i.e., elevated frontal alpha impacts executive function, etc.), while too little alpha may correlate with a lack of presence or anxiety.


Beta is associated with a state of thinking, mental, intellectual activity and outwardly focused sustained concentration. This is basically a ‘‘bright-eyed, bushy-tailed’’ state of alertness.  An excessively high frequency of beta brainwaves may be noted in anxious and tense states.

Beta is the state that most of the brain is in when eyes are open and the individual is listening and thinking during analytical problem solving, judgment, decision making and processing information about the world. If beta is deficient, either throughout the brain or in small areas, the brain may have insufficient energy to perform tasks at peer group standards.



Absolute Power

Absolute power is measured in microvolts.  It represents how much energy is present at a given site and in a given frequency range compared to the normative data.

Relative Power

Relative power is a measure of how much energy and one band/frequency holds in comparison to the other bands.  This is then compared to normative data.  Deviation from norms in a given band or region of the brain correlates with associated brain functions and symptoms.


Asymmetry metrics in the context of QEEG analysis refers to physiological differences between the two cerebral hemispheres and/or other regions of interest. Electrophysiological differences are key to healthy and flexible brain function.  Asymmetry metrics are a reflection of deviation from normative data.


Diffuse phase and coherence hypo- and hyperconnectivity suggest potential difficulty diversifying function and communicating in a timely manner in order to adapt to changing environments. This may result in impaired or decreased processing speed, ‘rigidity of thought,’ impulsive thinking, decision-making without all the required information and/or anxiety.

Connectivity dysregulation suggests poor inter-site communication and subsequent impaired cognitive efficiency.

Phase dysregulation suggests that the brain is not communicating information across regions in a timely manner. This may lead to impulsive thinking, decision-making without all the required information and/or anxiety.  Excessive phase means the signals arrive too early (meaning a slowing of connections) while deficiency means they arrive too late.

Hypercoherence correlates with less flexibility, hypocoherence correlates with less efficiency