This allows us to compare an individual’s metric to the QEEG database (also referred to as QEEG testing), thus indicating whether there exists a non-typical electrophysiological marker with regard to the population. Bottom image shows the current density power (uV2) in brain regions or areas (voxels) for the alpha frequency band, estimated from EEG using LORETA.Ī QEEG normative database contains a set of metrics computed from EEG and collected from a large number of individuals, large enough to be representative of the population. Top image shows 2D maps representing the absolute power (uV2) in different frequency bands. Brain maps at sensor level (top) and brain source level (bottom). Beta band: indicator of inhibitory cortical transmission, and associated with power increases during active concentration.įigure 2.Alpha band: involved in motor functions (over the motor cortex) and cognitive functioning.Theta band: involved in memory encoding and retrieval, and associated with power increases during drowsiness.Delta band: predominates during deep sleep.
Neuroscientific literature distinguishes delta, theta, alpha and beta frequency bands (Figure 1), and relates them with distinctive states ( Niedermeyer, 2005, Kropotov, 2010). The most studied QEEG metrics are the absolute and relative power in different frequency bands (and ratios of two bands). QEEG is frequently used in biomedical research for measuring the pre and post effects of mental-health interventions. This ultimately may provide electrophysiological markers of disorders such as ADHD, schizophrenia, major depression, traumatic brain injury, and obsessive-compulsive disorder. The Quantitative Electroencephalography or QEEG (a method within brain mapping techniques) consists of applying mathematical methods to the EEG data, mainly power spectral analyses, to obtain quantitative metrics that are associated with behavioral-cognitive brain funcitons. The electroencephalogram (EEG) records human brain electrical activity by electrodes placed over the surface of the scalp, which reflects underlying cortical activity, commonly referred to as “brain waves” ( Niedermeyer, 2005).
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