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

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 ercorrelated desynchronization of the wave amplitudes in all the bands , a decrease of alpha-index (percentage presence in epoch) and regular ity together with parallel increase of the indices and mean periods of Delta- and theta-waves. This generalized reaction has shown 'non-spec ific' dependence upon novelty and difficulty of the tasks and stimuli with certain 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 rhymes (MR) than in mental multiplication (MM). An increase of Fa ctor II. values (related to increase of the index, frequency and regul arity of beta-activity and called 'cortical excitation', CE) was more expressed during MR, whereas an increase of Factor III values (an incr ease of mean alpha-period and theta-index called 'active selective inh ibition', ASI) was characteristic of MM, the latter reaction being evi dent in the right hemisphere. During analysis of external sound stimul i and rhythmical clenching of a fist, an increase of Factor III values ; was accompanied by decrease of Factor II values in the motor activit y, such reciprocal reaction bring localized in the central areas contr alateral to the hand moved. Neuropsychological analysis suggests that CE correlates with associative and successively organized mental opera tions involving search for memory traces and ASI presumably relates to different aspects of mental selectivity such as simultaneous mental o perations, voluntary attention and mental automation, the latter two c ases being supported by parallel reduction of CE. (C) 1998 Elsevier Sc ience B.V.