Speech prosodic characteristics recorded by functional magnetic resonance imaging in healthy volunteers

Abstract

Many mechanisms for the brain organization of speech processes remain poorly understood now. Objective : to assess the structural and functional organization of speech prosody, by applying functional magnetic resonance imaging (fMRI). This technique allows non-invasive studies of the organization of the speech system. Patients and methods. Using their proposed three paradigms, the authors evaluated speech prosody in healthy volunteers. The first paradigm was aimed to determine the intonation characteristics of a sentence; the second paradigm is to study the given accentuated and non-accentuated rhythms, and the third to recognize melodies. Results and discussion. In the first paradigm, there was bilateral activation of Wernicke's speech area (Brodmann's Area 22) that significantly prevailed in volume and intensity in the right hemisphere of the brain. Also, the right hemisphere predominantly showed activation of the supplementary motor region included in cytoarchitectonical Brodmann's Area 6. There was a significant activation Brodmann's Area 9 when a rhythm was determined in the right hemisphere and in Brodmann's Area 46 when melodies were recognized. The cerebellum, limbic system, subcortical structures, etc. were noted to be activated, which permits speech function to be regarded as a whole brain process. Conclusion. The investigation has confirmed that different regions of both hemispheres of the brain are involved in the systemic organization of speech, which enables the authors to speak about the codominance of the hemispheres in respect of this function. The presented paradigms fully meet the objectives of the study and can be used to map the prosodic characteristics of speech.