P.K. Anokhin`s theory of functional systems supposes that interaction of some functional systems underlies a behavior act. These systems got into the interaction during so called afferent synthesis (AS) of the act. The present investigation undertakes to reveal the EEG- correlates of ASs related to performance of different choice tasks. Subjects (Ss) performed different choice tasks in two experiments. We used the procedure of increasing the number of active systems during AS, that allowed us to reveal the EEG-potentials related to AS. In the sensory-motor choice reaction time task two alternative stimuli were presented in random order and with equal probability. The stimuli were composed of two components - common warning signal (WS) and different determining signals (DS). Because of time intervals between WS and DS were different in these stimuli Ss predicted DS of one stimulus more correctly than another one. With the correct prediction of DS there are active only those systems in AS which will subserve the response on this DS. With erroneous prediction of DS there are active systems in AS which are related with predicted DS and which are related with presented DS. It has been found the relation between the number of active systems in AS and property of P300: increasing of a number of systems was accompanied by increasing in negative shift of the P300` s frontal slope. In the task of visual categorization of words Ss were presented in random order with one or other prime word (organism or object) followed by target word denotative the item belonging to organisms or objects. Ss have to press as quickly as possible one key if the prime and target were congruent and another key if these words were incongruent. In congruent case the systems related to one category of words were activated in AS wile in incongruent case the systems related to both categories of words were activated in AS. The frontal slope of P600 related to categorization were depend on whether the target word was congruent or on incongruent to the prime word. When the target word was incongruent to the prime word this frontal slope was more negative than when target word was congruent to the prime word.
Consequently, P300 related to response in choice reaction time task and P600 related to categorization of words are EEG manifestation of afferent synthesis.
Supported by РГНФ № 11-06-00917а; РГНФ № 13-06-00253а; НШ-3010.2012.6