SPATIOTEMPORAL DYNAMICS OF ALPHA-BRAIN ELECTRIC-FIELDS, AND COGNITIVEMODES

Brain electric activity is viewed as sequences of momentary maps of po tential distribution. Frequency-domain source modeling, estimation of the complexity of the trajectory of the mapped brain field distributio n in state space, and microstate parsing were used as analysis tools. Input-presentation as well as task-free (spontaneous thought) data col lection paradigms were employed. We found: Alpha EEG field strength is more affected by visualizing mentation than by abstract mentation, bo th input-driven as well as self-generated. There are different neurona l populations and brain locations of the electric generators for diffe rent temporal frequencies of the brain field. Different alpha frequenc ies execute different brain functions as revealed by canonical correla tions with mentation profiles. Different modes of mentation engage the same temporal frequencies at different brain locations. The basic str ucture of alpha electric fields implies inhomogeneity over time - alph a consists of concatenated global microstates in the sub-second range, characterized by quasi-stable field topographies, and rapid transitio ns between the microstates. In general, brain activity is strongly dis continuous, indicating that parsing into field landscape-defined micro states is appropriate. Different modes of spontaneous and induced ment ation are associated with different brain electric microstates; these are proposed as candidates for psychophysiological 'atoms of thought'. (C) 1997 Elsevier Science B.V.