The EEG signal consists of electrical oscillations with different rhythmical characteristics referred to as brainwaves. The brainwave spectrum reflects the individual’s state of arousal, or the ‘tone’ of the nervous system, and its analysis reveals the patterns of individual’s cortical information processing. Although operating in a continuous spectrum, brainwaves are commonly divided into frequency bandwidths to describe their function. These functional characteristics of the brainwaves, alongside with the loci of their generation lay in the core of the analysis we conduct as part of your qEEG brain assessment.
| 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 |
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 µV |
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 | |
| Activation
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) |
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 – 35 |
Perceptual and cognitive binding, insight, creativity, integration of new material, consciousness, mental clarity, efficiency, indicates speed of information processing |
