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HSE Scientists Use MEG for Precise Language Mapping in the Brain

HSE Scientists Use MEG for Precise Language Mapping in the Brain

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Scientists at the HSE Centre for Language and Brain have demonstrated a more accurate way to identify the boundaries of language regions in the brain. They used magnetoencephalography (MEG) together with a sentence-completion task, which activates language areas and reveals their functioning in real time. This approach can help clinicians plan surgeries more effectively and improve diagnostic accuracy in cases where fMRI is not the optimal method. The study has been published in the European Journal of Neuroscience.

The brain controls many functions, including movement, perception, memory, and language. When its functioning is disrupted by illness or injury and surgery is required, it becomes crucial to determine the precise boundary between the affected and healthy regions. 

Special attention is given to language-related regions, as their exact location varies across individuals and cannot be determined solely from anatomy. To identify these areas and avoid damaging them during surgery, clinicians perform language mapping to reveal which regions of a particular person’s brain support language functions. Functional MRI (fMRI) is typically used for this purpose: it shows brain activity during language tasks, but only indirectly, by detecting changes in the concentration of substances in the blood. If a patient has impaired blood flow, the results may be distorted.

A team of researchers at the HSE Centre for Language and Brain set out to determine whether language mapping could be made more accurate. For this, they used magnetoencephalography (MEG), a method that records the weak magnetic fields generated by neural activity. Unlike fMRI, MEG enables the measurement of brain activity directly and the tracking of changes with millisecond precision.

Selecting an appropriate task for such an experiment can be challenging, as it must reliably engage language processes while also being suitable for MEG recording. The team chose a sentence-completion task previously developed and validated by researchers at the HSE Centre for Language and Brain. In this task, participants read short sentences with the final word omitted and complete them aloud using a word that fits both semantically and grammatically. The task activates all components of the language system, from semantic processing to articulation. It was then technically adapted for MEG: the order and timing of stimulus presentation were modified to ensure accurate recording of brain activity at the relevant moments. 

The study involved 21 neurologically healthy native Russian speakers. While participants read and produced words, the device recorded their brain activity in the beta frequency range (17–25 Hz), which is associated with language processing. To ensure that the recorded signals truly reflected language function, the researchers added two control conditions: a passive condition (simply looking at the screen) and an active one (repeating simple syllables such as 'lo-lo-lo'). The comparison showed that the active control condition allows for a clearer separation of true language-related activity from unrelated background activity.

Differences in brain activity across tasks. The top panel shows the contrast between performing the sentence-completion task and resting, while the bottom panel shows the difference between sentence completion and syllable repetition. Sentence completion activates brain regions responsible for language comprehension and production, whereas syllable repetition engages more general processes that are not specific to language.
© Protopova M., Bolgina T., Arutiunian V., Dragoy O. Language Localization from Magnetoencephalography (MEG) Beta-Power Dynamics During Sentence Completion. European Journal of Neuroscience, 62(8): e70282, 2025.

Data analysis confirmed that the canonical language regions of the left hemisphere—the temporal and frontal areas involved in language comprehension and production—were activated during the task. Activity in these regions increased as participants progressed through each sentence: first, areas related to reading and semantic processing were engaged, followed by regions responsible for utterance planning and articulation.

Despite individual variability among participants, the overall pattern was consistent with findings from previous studies. This indicates that the Russian version of the sentence-completion task can be used for language mapping with MEG, and that the active control condition makes the results more robust and more closely aligned with clinical practice.

Maria Protopova

'We have demonstrated that combining MEG with the sentence-completion task makes it possible not only to identify the brain regions involved in language processing but also to track how their activity changes over time. We hope that in the future, this approach will help neurosurgeons more accurately determine the boundaries of language-related areas and lower the risk of language loss during surgery,' explains Maria Protopova.

The study was conducted within the framework of the Basic Research Programme at HSE University.

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