Study of the perception of written speech using functional tomography based on electroencephalography data

The spectral and spatial characteristics of the electroencephalograms recorded during the perception of written speech were studied. For the experimental study, four groups were formed, each containing 100 words: words with a positive emotional rating, words with a negative emotional rating, words with concrete meanings, and words with abstract meanings. A separate experiment was conducted for each group with the subjects. Words were represented by white text on a black background, each word was presented for 1000 ms, after the presentation of the stimulus there was a pause of 500 ms. Brain activity was recorded using an electroencephalograph with 19 leads, arranged according to the 10–20 scheme. For detailed quantitative analysis of this activity, method of functional tomography of the brain, based on electroencephalography data, was used. This method is based on the Fourier transform of multichannel encephalographic data and the localization of individual spectral components. The method makes it possible to single out and stably localize in space various spectral features of the brain activity studied in experiments on speech research. The frequency band from 8 to 30 Hz was analyzed; for all spectral components in this band, the inverse problem was solved in the approximation of an equivalent current dipole in a single-layer spherical conductor, without any restrictions on the position of the source. As a result, three-dimensional maps of activity were built - the functional structures of the brain. The presentation of these functional structures on magnetic resonance imaging allows one to study the frequency and spatial characteristics of responses to various speech stimuli.