ON THE INTERCORRELATION OF SOME FREQUENCY AND AMPLITUDE PARAMETERS OFTHE HUMAN EEG AND ITS FUNCTIONAL-SIGNIFICANCE - COMMUNICATION I - MULTIDIMENSIONAL NEURODYNAMIC ORGANIZATION OF FUNCTIONAL-STATES OF THE BRAIN DURING INTELLECTUAL, PERCEPTIVE AND MOTOR-ACTIVITY IN NORMAL SUBJECTS (VOL 28, PG 77, 1998)

In 95 normal subjects, a separate evaluation of the amplitude and freq uency parameters of EEG by period analysis made it possible to reveal, using factor analysis, four independent groups of parameters - the EE G factors, two of which being independent of the amplitude fluctuation s. They were considered as integral EEG characteristics of qualitative ly different neurophysiological processes. Decrease of Factor I values during mental activity (called 'general activation') reflected an int erconelated desynchronization of the wave amplitudes in all the bands, a decrease of a-index(percentage presence in epoch) and regularity to gether with parallel increase of the indices and mean periods of Delta - and theta-waves. This generalized reaction has shown 'non-specific' dependence upon novelty and difficulty of the tasks and stimuli with c ertain task-specific topographical distribution. An increase of values of regional Factor Ia in the anterior areas was caused by Delta- and theta-amplitude synchronization, more pronounced during matching the r hymes (MR) than in mental multiplication (MM). An increase of Factor I I values (related to increase of the index, frequency and regularity o f beta-activity and called 'cortical excitation', CE) was more express ed during MR, whereas an increase of Factor III values tan increase of mean alpha-period and theta-index called 'active selective inhibition ', ASI) was characteristic of MM, the latter reaction being evident in the right hemisphere. During analysis of external sound stimuli and r hythmical clenching of a fist, an increase of Factor III values was ac companied by decrease of Factor II values; in the motor activity, such reciprocal reaction being localized in the central areas contralatera l to the hand moved. Neuropsychological analysis suggests that CE corr elates with associative and successively organized mental operations i nvolving search for memory traces and ASI presumably relates to differ ent aspects of mental selectivity such as simultaneous mental operatio ns, voluntary attention and mental automation, the latter two cases be ing supported by parallel reduction of CE. (C) 1998 Elsevier Science B .V. All rights reserved.