In contrast to any other neuroimaging technique, only qEEG at the same time

• is the cheapest, fastest, and portable technique that measures neuronal activity directly and non-invasively;
• requires no overt cooperative behavior from the individual;
• independent of language, ethnicity, or cultural background, and stable from the age of 16 till 60 years;
• has very high test-retest (1 h – 5 years) reliability;
• is the most heritable bio-signal (genetic factors have a strong influence on qEEG variation);
• has temporal resolution adequate to mental and cognitive processes;
• may distinguish between excitatory and inhibitory neurons activation with the same metabolic demands;
• may distinguish between different temporal scales of information processing inherent to mental and cognitive processes.

Currently, there is common agreement in the field of cognitive neuroscience that qEEG does reflect conditions, functional properties and global states of brain functioning and is closely related to information processing and cognitive activity. The interaction of large populations of neurons gives rise to rhythmic electrical events in the brain, which can be observed at several temporal scales – qEEG oscillations. They are the basis of many different behavioural patterns and sensory mechanisms. qEEG oscillations are phylogenetically preserved, therefore they are functionally relevant.

Numerous studies have demonstrated that qEEG characteristics can confound functionally different psychophysiological determinants. Given the extensive scientific data on the frequency-dependent functional meaning of qEEG oscillatory activity, different aspects of qEEG oscillatory activity may help reveal which types of brain functioning are involved in mental activity.

In this context, qEEG is an accurate, unambiguous, ordered, stable reflection of the brain processes that underlie cognitive and mental activity. For more details and the review, see here.