Studies of the closed-eyes resting state provide an important opportunity to examine baseline EEG patterns unbiased by any task. The resting-state condition avoids the confounding effects of visual scenes, instructions, and task execution (i.e., expectation matching, strategies employed, motivation or lack of it, fatigue and anxiety associated with task performance). Additionally, resting state seems more self-relevant than standard cognitive tasks, which typically drive subjects to direct their attention away from their personal concerns. The resting-state condition permits assessment of “pure” self-relevant baseline brain activity. This activity reflects individual type of spontaneous processing of an internal mental context (top-down processing), such as random episodic memory and related imagery, conceptual processing, stimulus-independent thought, self-reflection, internal “narrative,” and “autobiographical” self. The frequently expressed concern that unconstrained brain activity varies unpredictably does not apply to the passive resting-state condition of the human brain. Scientific studies have shown that it is rather intrinsically constrained by the default functionality of the resting-state condition that comprises individual neurophysiological type.

In this context resting state EEG manifests the baseline mechanics of self-organization that regulates the multiple brain systems adapting the brain and body to an ever-changing environment. Thus, resting state EEG reflects intrinsic baseline/default activity that instantiates the maintenance of information for interpreting, responding to and even predicting environmental demands.

The human brain represents only 2% of total body mass but consumes 20% of the body’s energy, most of which is used to support resting ongoing neuronal signaling. Task-related increases in neuronal metabolism are usually small (<5%) when compared with this large resting energy consumption. These facts support the importance of resting state neuronal activity that consumes most of the brain’s energy.

The resting state constitutes a reference baseline, relative to which all cognitive and physiological states can be considered. Cognitively driven fluctuations cannot be interpreted except in the context of the default system. The default mode of brain activity at rest has a specific functional connotation with cognitive and emotional processes revolving around the subject’s internal state instead of current external events or circumstances.

Thus, patterns of resting state qEEG serve as a functional localizer (“context”), providing a priori information about the way in which the brain will respond across a wide variety of tasks and conditions (“content”).