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Abstract
The spontaneous EEG, viewed as a series of momentary scalp field maps, shows stable
map configurations (of periodically reversed polarity) for varying durations, and
discontinuous changes of the configurations. For adaptive segmentation of map series
into spatially stationary epochs, the maps at the times of maximal map relief are
selected and spatially described by the two locations of maximal and minimal (extreme)
potentials; a segment ends if over time an extreme leaves its pre-set spatial window.
Over 6 subjects, the resting alpha EEG showed 210 msec mean segment duration; segments
longer than 323 msec covered 50% of the total time; the most prominent segment class
(1.5% of all classes) covered 20% of total time (prominence varied strongly over classes;
not all possible classes occurred). Spectral power and phase of averages of adaptive
and pre-determined segments demonstrated the adequacy of the strategy, and the homogeneity
of adaptive segment classes by their reduced within-class variance. It is suggested
that different segment classes manifest different brain functional states exerting
different effects on information processing. The spatially stationary segments might
be basic building blocks of brain information processing, possibly operationalizing
consciousness time and offering a common phenomenology for spontaneous activity and
event-related potentials. The functional significance of segments might be modes or
steps of information processing or performance, tested, e.g., as reaction time.