ИСТИНА

Introduction. Decision making is defined as the process of choosing between two or more alternatives. This process can be carried out at different levels. Thus, D. Kahneman distinguishes two systems: system 1 (responsible for impulsive, spontaneous decisions) and system 2 ( responsible for rational solutions) (Kahneman, 2011). The decision-making process is fairly well studied in psychology and psychophysiology, however, the number of studies of this process at different levels is not so extensive, so the brain mechanisms are not well established. In our study, we attempted to research the electrical activity of the brain at different levels of decision making. Methods. The study involved 7 healthy right-handed participants aged 20 to 28 years. Matrices of schematic black-and-white images of various objects were presented. The study include three sessions. In the first session, an image of the subject were presented for 500 ms. After 700 ms, a 2x2 image matrix was presented for 1500 ms, in this matrix participant had to indicate the position of the previously presented object.In the second sesion, the 2x2 matrices were presented for 3000 ms with an 900 ms interval . It was required to select an image that is redundant (an analogue of the “Fourth Extra” technique). In the third session, just like in the second one, 2x2 matrices were presented, but it was necessary to choose the image that the subject liked more. Each series used 140 unique matrices. During the sessions of studies, EEG was recorded from 19 chanails (10-20% system). "Brainsys" program was used for EEG registration, processing and analysis. Results. Differences were revealed between the power of the delta oscillation (0,5 - 4 Hz) for three experimental conditions (see Fig. 1). In the control sesion, which required a decision at the perceptual level (correlation of the stored image and its selection from the presented ones), an increase in the power of the delta rhythm along the occipital and parietal leads is observed. In two experimental sessions requiring decisions (in the second series based on categorization and logical conclusions, in the third based on subjective preferences), the power of the delta activity was amplified in the frontal and fronto-central leads (especially in the second series) and was lowered in the occipital leads. The lateralization of the spectral power of the rhythm was also revealed when decision making process was based on subjective preferences. Discussion and conclusions. Our results are consistent with the literature: it has been shown that the power of the delta oscillation is enhanced in tasks that require more cognitive control and attention (Harmony, 2013). An increase in the power of the delta activity is also associated with the activation of working memory, which is required in the second session of our study (Başar et al., 1999). In addition, an increase in the power of the delta oscillation in the frontal leads and attenuation in the occipital leads is associated with a shift in attention to the task, abstracted from current sensory experience (Başar et al., 2000). Thus, in our study, we revealed the specificity of the electrical activity of the brain at the different levels of decision making. Performing a task requiring perceptual categorization is accompanied by an increase in the power of the delta activity in the occipital leads (which can be connected with Kahneman's system 1). When “moving away” from current sensory information and involving working memory in the process, the focus of delta activity shifts to the frontal parts of the brain (system 2). Decision making at the different levels of categorization affects the severity of the delta oscillation.