Andrey O. Shevchenko

Relevance. The problem of identifying the cerebral mechanisms of internal speech (spoken words or even individual sounds — phonemes) based on the electrical activity of the brain is relevant and significant for a number of practical applications, in particular for improving the construction of brain-computer interfaces.

Target. Electroencephalographic research is aimed at identifying the cerebral mechanisms of internal speech, taking into account the modality of its initialization.

Methodology. In a study on 25 subjects, a 19-channel EEG was recorded in the process of performing three tasks on perception and internal pronunciation of seven phonemes of the Russian language: A, B, F, G, M, R, U, which were presented visually (in the form of letters) and audibly. The analysis of the obtained EEG data was carried out using a new author's method of localizing brain activity “virtually implanted electrode” (developed by A.V. Vartanov), which allows, according to scalp EEG data, to reconstruct electrical activity, the source of which is located in a certain place inside the head (activity was studied in 33 different points of the brain).

Results. The averaged evoked potentials were obtained for all the studied areas of the brain and the functional connections of these structures were revealed in the form of connectivity graphs for the corresponding conditions.

Conclusions. It was found that the processes of pronunciation, expressed in EP, differ depending on the modality of the initial form of the reproduced image — in visual perception, the supromarginal gyrus is more involved. The synchronized activity of a number of cerebral zones providing internal speech was revealed. A special role is played by the activity of the hippocampus and the pallidus (Gl. Palidus). The form of the EP when perceived is in many ways similar to its form when pronouncing. Activation at visual input is almost always significantly higher than at auditory input.