From Mapping to the Analysis and Interpretation of EEG/EP Maps

The organization of the neuronal activity of the brain varies over time, depending on determinants such as maturational stage, circadian activity cycle, metabolic condition, motivational state, newly arriving information in conjunction with related, past context experiences, drugs, and disease (Koukkou et al. 1980). A every moment in time, there exists a particular global, brain functional state which is the consequence of the interaction between newly received information (Koukkou-Lehmann 1987) and spontaneous (“housekeeping”) activity. In turn, the momentary functional state (Koukkou and Lehmann 1983) constrains and shapes the elaboration of, and the responses to newly arriving information, and constrains and shapes access within the brain to information-processing strategies and to context information which was stored earlier (“state-dependent learning and recall”). Classical examples are wakefulness and sleep, or childhood and adulthood, with their different modes of information processing. These gross functional states ough to be seen as composed of local and temporal microstates. A global brain state is thus made up from a large number of local, mementary states of the various cortical and subcortical functional analyzers and processors (Koella 1982). Concerning the temporal dimension, there is good evidence that as a consequence of newly arriving information, series of different, brief brain states are initiated which manifest different steps and aspects of the processing of the information, and which are referred to as “components” in evoked potential/event-related potential (EP) work. Likewise, “spontaneous” EEG activity is hypothesized to consist of a sequence of similarly brief epochs of stationary spatial electric patterns (maps) which manifest different functional states (Lehmann et al. 1987).