Cerebral organization of verbal action in stutterers

Abstract

The theory of systemic dynamic localization of mental functions developed by A.R. Luria [1] analyzes all factors of the speech functional system in detail with the exception of readiness for speech, mentioned without considering its localization [2]. Disruption of this factor, involved in the centrally controlled tuning of the peripheral speech apparatus for a verbal act, is considered in defectology as the main mechanism of stuttering [3]. In addition, intra-and interhemispheric interactions during the verbal activity of stutterers are poorly known, although many authors have mentioned that disintegration of these interactions during psychic activity may be one of the mechanisms of stuttering [4][5][6][7][8][9][10][11]. When stuttering begins in early childhood, the formation of hemispheric specialization in performing both sensory (of all modalities) and verbal functions is interrupted [12].Some authors hold that stuttering is only a motor problem; some others believe that it is caused by disruption of the higher level of organization of cognitive and motor processes. In our view, a combination of neuropsychological and psychophysiological methods may clarify the localization of the mechanism of readiness for speech and its connection with neuropsychological patterns of cognitive disorders in stutterers.Our purpose was to study the cerebral mechanisms of stuttering with a comprehensive set of neuropsychological and psychophysiological methods. First of all, we were interested to learn how the statement preparation mechanism functions and how it is affected in stuttering. METHODSThe following methods were applied in the study:(1) comprehensive neuropsychological examination according to Luria [13] with qualitative and quantitative evaluation of the data [14], (2) study of the lateral organization of sensory and motor functions (dichotic listening [15] and a modified version of the questionnaire and tests related to the lateralization of mental functions [16]), (3) recording of potentials related to the moment of pronunciation of sounds of Russian speech, and (4) dipole localization of the sources of the electrical activity of the brain [17] and special methods of preliminary processing of the EEG [18].We examined ten stutterers and seven normal subjects aged 15-25 years, right-handers with a secondary or incomplete higher education. Four sounds of Russian speech ([a], [o], [r], and [l]) were reproduced by a computer from prerecorded sound files through a speaker. The duration of each presentation was 150 ms.We will consider the procedure of psychophysiological examination (methods (3) and (4)) in detail. Verbal stimuli were presented with a tape recorder to a subject, who sat in a chair at rest. The subject was instructed to reproduce each stimulus 1-2 s after the presentation. The moment when the sound was pronounced was recorded with a microphone with a special amplifier, and then the signal of exceeding a preset threshold was fixed as a label in the EEG record. The next stimulus was presented 3 s after the s...

Neuropsychological parameters as possible indicators of speech fluency disorder in children

“…Findings from modern neurodiagnostic techniques have implicated cortical and subcortical structures with PWS. Electroencephalographic measurements demonstrated greater activity in the nondominant right hemisphere in subjects with PWS during the speaking condition 20 . No such brain activity was reported in individuals without stuttering.…”