[Brain mechanisms of the semantic analysis of words-homonyms].

The brain mechanisms of semantic comprehension of a word were comparatively studied in three experimental conditions: simple perception of the nuclear value of a word-homonym determined by the preceding context, perception of its circumferential value, and during active semantic analysis of these values. It was shown that the amplitude of the evoked potential component P200 was correlated with complexity of the semantic analysis. A decrease in this amplitude under conditions of complication of semantic problem was associated with an increase in the activities of the caudate nucleus and hippocampus and a parallel slight decrease in the activity of cortical areas.

[The multifactor method of EEG separation into the cortical and deep components]. / Mnogofaktornyi metod razdeleniia EEG na korkovuiu i glubinnuiu sostavliaiushchie.

A new method of separation of multichannel brain electrical activity into cortical and subcortical components with the help of multifactor analysis is proposed. The method provides a means for isolation and, consequently, more reliable localization of sources of electrical activity not only in deep brain structures (on the basis of the dipole model) but also on the cortical surface. The proposed method does not depend on the rotation and interpretation of factors, and no data losses occur. The mufasel algorithm is based on integration of all selected factors (within a particular EEG or EP time segment) in two groups using a statistical criterion, which defines general and specific factors. It is assumed that general factors loaded with highly correlated derivations predominantly describe the electrical activity of deep brain structures, whereas specific factors loaded by the dynamics of electrical activity in individual derivations, reflect the integrated activity of cortical brain structures.

[Operative memory and evoked visual potentials]. / Operativnaia pamiat' i zritel'nyi vyzvannyi potentsial.

Changes in human EEG and event-related potentials to the complex color stimulus were studied during performance of three cognitive tasks: passive viewing, visual searching, and memorizing and storing of the stimulus in the operative memory. It was shown that involvement of memory mechanisms resulted in the alpha rhythm suppression in both occipital and frontal brain areas. It was also accompanied by a generation of the slow positive component in the evoked potential recorded in the frontal areas (in the occipital areas this wave was manifested as negative).

[A model of color vision in trichromats and protans]. / Model' tsvetnogo zreniia trikhromatov i protanov.

A model which explains the human vision protanopic deficiency and its biologic prototype with the absence of red-absorbing pigment (rabbit) was constructed from neuron-like elements. In behavioral experiments and by means of evoked potential technique it was shown that the rabbit's color space is characterized by a spherical four-dimensional with a reduction of red-coding area. Similar spherical four-dimensional structure of color space is characteristic for a group of protanopic human subjects. The perceptive space of another group of protanopic subjects (protanomals) is characterized by a reduction of both parts of the red-green opponent axis. These disorders are reproduced in the model either by a loss of some color-coding elements (the absence of the red-absorbing pigment as in protanops) or a shift of the spectral characteristics of the red pigment towards those of the green one (protanomals).

[The emotional characteristics of the sounding word]. / Emotsional'nye kharakteristiki zvuchashchego slova.

The four-dimensional spherical emotional space has been obtained by multi-dimensional scaling of subjective differences between the emotional expressions in sound samples (the words "Yes" and "No" pronounced in different emotional conditions). Euclidean space axes are interpreted as the following neural mechanisms. The first two dimensions are related with the estimation of a sign of emotional condition: the dimension 1--pleasant/unpleasant, useful or not, the dimension 2--an extent of information certainty. The third and the fourth axes are associated with the incentive. The dimension 3 encodes active (anger) or passive (fear) defensive reaction, and the dimension 4 corresponds to achievement. Three angles of four-dimensional hypersphere: the one between the axes 1 and 2, the second between the axes 3 and 4, the third between these two planes determine subjectively experienced emotion characteristics such as described by Vundt emotion modality (pleasure-unpleaure), excitation-quietness-suppression, and tension-relaxation, respectively. Thus, the first and the second angles regulate the modality of ten basic emotions: five emotions determined by a situation and five emotions determined by personal activity. In case of another system of angular parameters (three angles between the axes 4 and 1, 3 and 2, and the angle between the respective planes), another system of emotion classification, which is usually described in the studies of facial expressions (Shlosberg's and Izmailov's circular system) and semantics (Osgood) can be realized: emotion modality or sign (regulates 6 basic emotions), emotion activity or brightness (excitation-rest) and emotion saturation (strength of emotion expression).

[The characteristics of the color perceptive space in protanomals]. / Osobennosti tsvetovogo pertseptivnogo prostranstva protanomalov.

Color vision of three protanomal subjects was studied by means of direct paired comparison technique using 25 colors with different brightness. It was shown that the characteristics of their color vision could be completely and adequately described in the frames of the four-dimensional spherical model of color perception. The spatial axes could be identified as the two color-opponent mechanisms (red-green and blue-yellow) and the two achromatic mechanisms (brightness and darkness). Deformation of the color axes in protanomals (as compared with the normal trichromatics) was demonstrated in the "red" and "yellow" spectral region. The visual disturbance in protanomal subjects involves not only color but also achromatic mechanisms. This is manifested in the a deformation of perceptual brightness scale. In comparison with normal trichromatic subjects, the protanomals perceive the red and adjacent colors as achromatic while green, yellow-green, and orange as more bright but low-saturated colors.

[The discrimination of color images in human operative memory]. / Razlichenie tsvetovykh obrazov v operativnoi pamiati cheloveka.

Qualitative changes of color image maintained in the operative memory were studied using the modified Sperling's strategy. On the basis of estimations of difference between any two color images (from nine possible), contained in the same memory volume within 50 and 100 ms, the respective mnemonic spaces were built and afterwards correlated with the perceptual and semantic spaces. It was found out that the maintenance of a color image in the operative memory was affected by two simultaneous but independent factors. The first factor described the fading, i.e., extent of the intensity loss of the primary color image in the process of its maintenance in the operative memory. Fading was accompanied by a decrease in the signal-to-noise ratio and increase in the incidence of the casual mistakes in comparing the images with each other. The second factor determined the systematic transformation of color images in the memory expressed in the effect of clusterization of point stimuli and specific change in the between-point distances (estimations of difference).

[The retention of a color image in short-term memory]. / Sokhranenie tsvetnogo obraza v kratkovremennoi pamiati.

The article deals with the study of the dynamics of retention of a colour image in the short-term memory by a technique of multidimensional scaling under conditions of delayed administration of a second stimulus in a pair. Comparison of colour spaces of the short-term memory (delays of 4, 15, and 60 sec) with the perceptive space without any delay showed that the four-dimensional spherical structure of the colour space remained stable, but the accuracy of assessments decreased with increase of the delay time. This led to a deterioration of the metrical determinacy of the space and an increase in the thickness of the spherical layer.

[The role of the first and second signal systems in the correlation of semantic and perceptive color spaces]. / Rol' pervoi i vtoroi signal'nykh sistem v sootnoshenii semanticheskogo i pertseptivnogo tsvetovykh prostranstv.

The first and the second signal systems were studied in computerized experiments using colour stimuli and colour names. Multidimensional graduation of subjective differences between monochromatic colours and colour names showed that perceptual colour space and semantic colour space were isomorphic and constituted hyperspheres in a four-dimensional space. The angles of the hypersphere corresponded to hue, lightness, and saturation of colours and ordered colour names with respect to these characteristics. The subjective differences between monochromatic colours and colour names made it possible to construct a common space where monochromatic colours and corresponding colour names were represented by the neighbouring points, thus supporting isomorphic relations between perceptual and semantic colour spaces.