Two complementary components of language grammar are being studied: structural, or static (which brain areas are necessary for language processing? how is language related to other psychological processes?), and functional, or dynamic (how are brain areas functionally connected? how is language processed in real time?). The examination of each of these components is approached from two perspectives: from the point of view of the psychology of processing and from the point of view of the brain substrate implicated in it. Such approach to the study of grammar, which constitutes the core of the human language, provides a most comprehensive and detailed scientific understanding of language, its psychological mechanisms and the brain substrate underlying its processes. Furthermore, due to such approach, the outcome of the present research will be of high relevance to the international scientific community and will provide important contribution to the field.
The objective is to demonstrate psychological organization and neural basis of language grammar, and to reveal how they interact dynamically with other cognitive functions. The specific research tasks include identifying which brain areas are critical for realization of language and its distinct grammatical components (structural-anatomical aspect of language); how language and its grammatical components are related to other cognitive functions (structural-psychological aspect); how different brain areas that are involved in language processing interact and communicate between each other (functional-anatomical aspect); and, finally, how language components under consideration function in real time (functional-psychological aspect).
Methodology. The present research employs state of the art methods from contemporary linguistics and neuroscience. In order to examine the structural-anatomical properties of language processing, two methods of structural neuro-visualization were used: voxel-based lesion-symptom mapping and tractography. The primary methods for examining functional-anatomical aspects of language constituted functional magnetic resonance imaging and direct electrical stimulation of the brain during neurosurgery. Structural-psychological and functional-psychological aspects of language were examined with various behavioral methods, such as self-paced reading paradigm, sentence-picture matching, eye-tracking.
Empirical base of research. Empirical base of research is represented by a series of neurolinguistic experiments targeting the four aforementioned aspects of language processing. Healthy subjects as well as patients with language disorders of organic nature and different etiology took part in the experiments. Patient group did not only comprise patients with post-stroke aphasia, but also patients with pharmacoresistant epilepsy in order to examine the role of temporal lobe in language processing, and patients with brain tumor in order to examine the naming function with the help of the method of intraoperative direct electrical stimulation.
Results of research. The outcome of the present research includes important knowledge obtained across a series of experiments that answer the questions about which brain areas are critical for realization of distinct components of language grammar, which unifying psychological principle underlies these grammar components and other cognitive functions, how language-related brain areas are interconnected, and how the grammar components under examination function in real time. The results are described in six research articles written in English and published in international peer-reviewed journals.
Recommendations on implementation of the results. Application of the findings of the current research is related to the gained insights about psychological and neural mechanisms of grammatical processing in healthy people and people with language pathology, as well as to the implementation of the methodological apparatus in the clinical practice. Recommended methodology can be used in future fundamental investigations of language and can be adapted in the clinical practice for improvement of existing language diagnostic tools and speech rehabilitation.
The areas of implementation of the results involve fundamental and applied studies of language, as well as rehabilitation of speech in patients with brain damage. The obtained findings can serve as a foundation for future empirical research endeavors that aim to identify new neural manifestations of language in other populations of language users. Finally, they can provide a basis for the development of new practical tools for language diagnosis and rehabilitation.