The spatial organization of biopotentials in the cerebral cortex of 23 subjects who were students at the Faculty of Graphic Arts ("professionals") as well as 39 subjects lacking systematic experience of visual images ("non-professionals") was compared with the aim of identifying EEG correlates of the experience of visual images (image formation) in humans. Changes in measures of the spatial organization of biopotentials (spatial synchronization, spatial disordering, coherence, and spectral power) were analyzed as subjects mentally composed visual images consisting of two simple graphic elements - right angles and oblique lines. The total number of image elements increased in each of four sequential tasks, from a number which could be analyzed at the conscious level (4-7 elements) to a number exceeding analysis at the conscious level (8-16). Intergroup differences, particularly increases in the spatial disordering of biopotentials (non-linear processes), were detected when large numbers of elements were used (tasks 3 and 4). This measure increased more markedly in professionals than in non-professionals. Changes were significant in the anterior areas of the right hemisphere. Spatial synchronization of biopotentials (linear processes) increased in non-professionals in the posterior areas of the right hemisphere. Coherence and spectral power increased in professionals in a larger number of narrow-band EEG frequency subranges than in non-professionals. These data show that experience of visual imagery results in a more complex neurodynamic process during the activity, with non-linear dynamics and a multitude of EEG resonance systems at different frequencies.

The within-pair similarity of the topographical maps of the spatial synchronization of the cerebral cortical potentials was studied in 11 pairs of monozygotic twins and 20 genetically unrelated subjects in the resting state and during four types of intellectual activity. It was demonstrated that the degree of similarity of the topographical maps is higher in the resting state in the monozygotic twins than in the genetically unrelated subjects. No frequency band of the EEG which exerts a special influence on the formation of the high degree of similarity of the spatial synchronization of the potentials was found. The maximal similarity in the topographical maps of the monozygotic twins is observed in the anterior regions of the left hemisphere and in the temporoparietal regions of the right. Differences between groups are recorded in both regions; however they are especially distinct in the right hemisphere. The data obtained make it possible to draw an inference regarding the influence of a genetic factor not only on individual components of the EEG (which had been previously demonstrated by a number of authors), but also on the systemic organization of the cortical processes. The right-hemispheric activity apparently relates to the most controllable genetic processes. The results of the analysis of the similarity of topographical maps during various types of activity confirm this: the coefficient of similarity reaches the level of significance in the majority of pairs of monozygotic twins only in a "right-hemispheric" test (simultaneous analysis of nonverbal material).

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The characteristics of the spatial organization of biopotentials in the neocortex during the mental creation of original and standard mental images were studied. Intra-and interhemisphere coherence associations at different EEG frequency ranges were assessed, along with linkages between relative changes in measures of linear (correlation coefficient) and non-linear (multiple entropy) processes between different areas of the neocortex. Creation of original thoughts was found to be associated with a significantly smaller number of associations with decreased coherence in the high-frequency alpha range between distant points than on formation of standard images. On formation of original images, the number of concordantly functioning pairs of cortical areas and the mean level of synchronization between them were greater in terms of linear processes than on formation of standard images, while in terms of non-linear processes, the number was, conversely, smaller. The correlational relationships between changes in different cortical areas for both types of process were only positive on creation of original images, while creation of standard images yielded both positive and negative correlations. These data lead to the conclusion that the spatial organization of biopotentials during the mental creation of original and standard images differs in terms of the cortical distribution of concordant changes in linear and non-linear processes, their levels of linkage, and the nature of interhemisphere interactions. Data on differential interhemisphere interactions in the diagonal and central bilateral profiles suggest the radial representation of visual imagination.

Theoretical questions of the spatial organization of electrical activity in the brain are discussed in terms of a multilevel realization of the synergetic principle for formation of functional systems underlying behavior and mental function. The role of the spatial-temporal superimposition of coherent structures of biopotentials in generating fields of increased activity in the cerebral cortex is discussed, these being responsible for integrative and associative functions. A hypothesis is proposed regarding the relationship between the energy and information factors of coherent structures as one of the important characteristics describing the efficiency of energy-informational processes. Emphasis is placed on the need for considering not only linear, but also nonlinear associations of biopotentials in considerations of the form and functional sense of their spatial organization.