Organization and current understanding of speech function of the brain: literature review

Introduction. History of study of speech function of the brain has started in the middle of the 19th century. First studies discovered cortical representations of speech in the brain, proposed different theories of speech function structure. Technological breakthroughs of the 20th century allowed to study not only cortical representations of speech function but also complex connections of the white matter important for practical work of neurosurgeons. Deeper studies of speech led to revisions of the old theories, proposals of new theories. Current study methods showed complexity of speech organization, multifunctionality of speech tracts.Aim. To analyze and systemize historical and current scientific data on organization of speech function of the brain, as well as methods of preoperative evaluation and intraoperative techniques of identification of speech zones in the cerebral cortex.Materials and methods. As a results of data search in the PubMed database, 77 articles published between 1954 and 2020 were selected.Results. Studies of characteristics of speech function are widely represented in current scientific literature, and their number grows every year. Some researchers study individual speech aspects: cortical representation, individual speech tracts. Others deal with general consequences of speech impediments after tumor resection, strokes, traumas. The authors cross-linked and systemized numerous data from different sources of information.Conclusion. Speech function of the brain is one of the most complexly organized aspects of the higher nervous function, and it is being actively researched worldwide. Implementation of such revolutionary examination techniques as intraoperative mapping of the cerebral cortex, magnetic resonance tractography provided a plethora of new information on morphofunctional characteristics of speech function. Further studies of speech function of the brain and systematization of the obtained data are necessary for deeper understanding of the details of speech organs' functionality. Advances in this direction will help surgeons avoid unwanted neurological deficit in communication ability, one of the most important abilities, and improve patients' quality of life.