Researchers have developed a method in the Russian language for preoperative mapping of language areas

Summary: Researchers have developed a Russian-language protocol for neuroimaging that maps individual linguistic areas of the brain prior to neurosurgery.

Source: HSE

Neurolinguists from HSE University, together with radiologists from the National Medical and Surgical Center in Pirogov, have developed a Russian-language protocol for functional magnetic resonance imaging (fMRI) that maps individual language areas before neurosurgical operations.

The study was published in Frontiers of Human Neuroscience.

When neurosurgeons operate on brain tumours, their objective is to remove the pathological tissue while preserving as much as possible the adjacent areas critical to the various motor and cognitive functions, including language.

The ability to preserve language areas determines whether the patient will have language impairment after the operation and will be able to communicate easily with others, hold a job and lead an ordinary life.

The exact location of language areas differs from person to person, so special methods must be used to map them in each patient. The most accurate method is direct electrical stimulation during neurosurgery. But sometimes the neurosurgeon needs to know in advance where the language areas of a particular patient are to make the best possible plan for the operation. This preoperative mapping is carried out using a functional MRI, or fMRI.

While in an MRI scanner, the patient performs language-related tasks. Data analysis shows which areas of the brain are activated.

Until now, most protocols for preoperative linguistic mapping by this method were developed in English. Scientists from HSE University have developed the first Russian-language fMRI protocol that uses a language task recommended by the international scientific community: sentence completion.

The patient should read aloud a sentence with the last word missing (such as “The audience watched a long time…”) and then end the sentence with an appropriate word (such as “play” or “movie”). This task is unique in that it involves both language production and sentence-level comprehension, which allows for comprehensive mapping of the patient’s language areas.

The researchers validated the protocol in a control group of 18 healthy Russian-speaking volunteers aged 30 to 53. This proved that the protocol successfully maps the most important linguistic areas in the frontal and temporal lobes of the brain and reveals the individual lateralization of linguistic function, i.e. the extent to which this function relies on the hemispheres left and right brain. .

Regions of interest used in the analysis. (A–C) Frontal, temporal-parietal, and frontal-temporal-parietal regions of interest used in the analysis of Dice’s coefficients and lateralization indices. (D) Eight language-related regions of interest based on the Brainnetome atlas (Fan et al., 2016) implemented in the ICN_atlas toolkit (Kozák et al., 2017), used to assess activation at the individual level. White: pars triangularis of the inferior frontal gyrus; blue: pars opercularis of the inferior frontal gyrus; green: posterior middle frontal gyrus; burgundy: additional motor area; red: posterior middle temporal gyrus; cyan: posterior superior temporal gyrus; beige: supramarginal gyrus; yellow: angular gyrus. Credit: The Researchers

The researchers also demonstrated the high reliability of the protocol: each volunteer underwent the procedure twice with an interval of several weeks and the results were similar. This is the first protocol in the Russian language that has undergone such extensive validation.

Svetlana Malyutina, researcher at the HSE Center for Language and Brain and co-author of the article, says that “the first stage of the study has been completed, showing the validity and reliability of the protocol in the control group. We are now doing the most important part: testing the protocol in clinical practice, using it for preoperative voice mapping in patients with brain tumors and epilepsy.

“We plan to analyze whether the protocol works equally well in the clinical groups as in the control group. We will test to what extent its results match those of intraoperative mapping and, therefore, to what extent it should be applied in clinical practice.

About this news about brain mapping and language research

Author: Press office
Source: HSE
Contact: Press office – HSE
Picture: The image is attributed to the researchers

Original research: Free access.
“A new functional magnetic resonance imaging locator for preoperative language mapping using a sentence completion task: validity, choice of baseline, and test-retest reliability” by Kirill Elin et al. Frontiers of Human Neuroscience


Abstract

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A novel magnetic resonance imaging functional locator for preoperative language mapping using a sentence completion task: validity, choice of baseline, and test-retest reliability

To avoid post-neurosurgical language deficits, intraoperative mapping of language function in the brain can be complemented by preoperative mapping with functional magnetic resonance imaging (fMRI). The validity of an fMRI “language locator” paradigm crucially depends on the choice of an optimal language task and a baseline condition.

This study presents a novel fMRI “language locator” in Russian using overt sentence completion, a task that comprehensively engages language function by involving both word- and sentence-level production and comprehension. .

The paradigm was validated in 18 neurologically healthy volunteers who participated in two scanning sessions, to estimate test-retest reliability. For the first time, two baseline conditions for the sentence completion task were compared.

At the group level, the paradigm significantly activated language-related anterior and posterior regions. Individual-level analysis showed that activation was triggered most consistently in the inferior frontal regions, followed by the posterior temporal regions and the angular gyrus. The test-retest reliability of activation location, as measured by Dice’s coefficients, was moderate and therefore comparable to previous studies.

Test-retest reliability was higher in the frontal than temporoparietal region and with the most liberal statistical thresholding compared with two more conservative thresholding methods. Lateralization indices were expected from the left hemisphere, with greater lateralization in the frontal than temporoparietal region, and showed moderate test-retest reliability.

Finally, the pseudoword baseline elicited more extensive and reliable activation, although the syllable baseline appears more feasible for future clinical use. Overall, the study demonstrated the validity and reliability of the sentence completion task for mapping language function in the brain.

The paradigm has yet to be validated in a clinical sample of neurosurgical patients. Additionally, the study contributes to the overall evidence on the test-retest reliability of fMRI.

Sylvester L. Goldfarb