The EEG signal consists of electrical oscillations with different rhythmical characteristics referred to as brainwaves. Careful analysis of the brainwaves’ morphology, speed, location and synchronicity can inform us about the individuals’ state of arousal, patterns of cortical information processing and emotion regulation.

Although operating in a continuous spectrum, brainwaves are commonly divided according to their speed into frequency bandwidths to describe their function. The frequency of the brainwaves, alongside with their morphology and  loci of generation lay in the core of the analysis we conduct as part of your qEEG brain assessment.

Below is a crude summary of the most commonly identified brainwaves, their electrophysiological characteristics and their functional significance

Activation Processing Origin EEG Rhythm Frequency (Hz) and Amplitude (µV) Oscillations implicated in:
Relaxation and Drowsiness

Global processing mode

Deep cortical layers-V, VI

Delta ~ 0.5  – 3.5

100- 200 µV
brainwave delta

Glial cells, deep sleep, early development, developmental pathology, brain tissue damage, anhedonia, under arousal, deactivation, need for reinforcement, basic motivational processes, autonomic nervous system, pain, homeostasis, signal-to-noise ratio in cortical processing, toxicity, injury
Theta ~   4 –   ~ 7

50- 100 µVbrainwave theta

Limbic system activity, emotions, memory retrieval, drowsiness, day-dreaming, inattention, event-related potentials, trauma
Alpha and Mu ~   8 –  ~ 12

30- 50 µV.

Thalamo-cortical idling rhythm of the visual system, normally attenuated when eyes open. Involved in relaxation, attention and focus, learning and perceptual readiness; Mu is an idling rhythm of the motor system, attenuated when performing a movement; frontal alpha asymmetry is implicated in mood

Local processing mode

Surface cortical layers- I,II,III

Low Beta and SMR ~ 12 – ~ 15

about 30 microvolts (µV)

Thalamo-cortical rhythm; resting rhythm of the motor system intention to remain still, mental alertness and physical relaxation; resistance to stress; excessive 12-15Hz -> anxiety, fibromyalgia and chronic pain conditions
Beta ~ 13 – ~ 21

about 30 microvolts (µV)beta brainwave

Cortical rhythm; sustained attention, thinking, problem solving, decision making, alertness
High Beta ~ 20 –  ~ 30

about 30 microvolts (µV)

Activation, over arousal, anxiety, stress, panic attacks, intense ruminations, agitation, obsessive thinking when over the cingulate
Gamma ~ > 30 – 35gamma Perceptual and cognitive binding, insight, creativity, integration of new material, consciousness, mental clarity, efficiency, indicates speed of information processing