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The cerebellum, a structure in the hindbrain, was long considered primarily responsible for motor control, balance, and coordination. Although it accounts for only about one-tenth of the brain's total volume, it contains up to 80 % of all neurons. This striking disparity suggests that its computational capacity serves far more than just movement. Modern neuroscience increasingly shows that the cerebellum also plays an important role in thinking, language, and emotional processing.

"The concept of the so-called universal cerebellar transformation suggests that the cerebellum applies the same type of computation to all incoming information, regardless of whether it originates from motor or cognitive brain regions. The goal of this process is to ensure fluency and automation. When the cerebral cortex initiates an action, such as moving a hand or forming a thought, it sends an efferent copy of this command to the cerebellum," explains Igor Riečanský, Head of the Department of Behavioural Neuroscience at the Institute of Normal and Pathological Physiology, Centre of Experimental Medicine, SAS.

Based on prior experience, the cerebellum generates predictions about the expected sensory or cognitive outcome of an action and compares them with the actual result. "If a discrepancy is detected, a prediction error signal is sent back to the cerebral cortex. This allows for immediate correction of the action while also updating the internal model for future situations, which is essentially a form of learning," he adds.

In the cognitive domain, the cerebellum supports executive functions such as working memory and planning. "While the cerebral cortex generates thoughts, the cerebellum helps organise their sequence. When this interaction is disrupted, a condition known as cognitive dysmetria may arise, characterised by reduced fluency and accuracy of thought processes. A similar principle applies to language: the cerebellum not only controls the muscles involved in speech, but also helps anticipate grammatical structures and facilitates word retrieval, ensuring fluent communication," explains Riečanský. These conclusions are supported by the institute's recent research using non-invasive brain stimulation (tDCS).

Findings from recent research

"In our study, healthy participants performed two types of tasks during stimulation. In the first, they were asked to quickly produce the first word that came to mind in response to a stimulus (automatic recall). In the second, they had to generate an unrelated concept, which required suppressing automatic responses (controlled recall).

Temporary modulation of cerebellar activity selectively impaired automatic recall, while controlled recall remained unaffected. This confirms that the cerebellum plays a key role in fast and automatic access to well-learned knowledge," Riečanský summarises. The results were published in the journal Neurobiology of Language.

"Research also shows that the cerebellum contributes to emotional regulation by helping fine-tune emotional responses to a given context, for example, in social situations. Damage to the cerebellum can lead not only to motor and cognitive impairments, but also to emotional flattening, mood disorders, or impulsivity, collectively referred to as cerebellar cognitive-affective syndrome," the scientist describes.

A new perspective on mental disorders

These findings also offer new insights into the mechanisms underlying certain mental disorders. The cerebellum is involved in processes related to inner speech and the sense of authorship of one's thoughts. "In schizophrenia, impaired processing of these signals may cause individuals to perceive their own thoughts as external voices, resulting in auditory hallucinations. Effective social interaction relies on the ability to predict others' behaviour rapidly. If the cerebellum fails to generate reliable predictions, social situations may become difficult to interpret, which may contribute to the development of autism spectrum disorders," the scientist states. Difficulties in predicting and filtering sensory input may also explain the sensory overload often experienced by individuals with autism, who may cope with it by relying on strict routines.

"The cerebellum can no longer be viewed solely as a centre for motor coordination. It should be understood as a key integrative structure that continuously anticipates and fine-tunes information, ensuring the smooth functioning of both our physical and mental processes," concludes Igor Riečanský.

Source: Igor Riečanský, Institute of Normal and Pathological Physiology, CEM SAS

Prepared by: Andrea Nozdrovická

Photo: canva.com