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Brain-periphery couplings and their contribution to motor control

par Mongold, Scott Jason
Président du jury Baudry, Stéphane
Promoteur Bourguignon, Mathieu
Publication Non publié, 2025-02-06

Thèse de doctorat

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Résumé :

Over the last three decades, substantial work in theoretical and applied neuroscience has led to the notion that the coupling between signals of the brain and the periphery sets the basis for motor communication. Two major coupling indices dominate the literature: corticomuscular coherence (CMC) and corticokinematic coherence (CKC). Importantly, CMC is thought to reflect efferent signaling and CKC, afferent signal processing, although there remains substantial debate. Yet, the question remains as to whether these forms of coupling lay the foundation for motor behavior; that is, does coupling strength influence one’s motor ability? Besides, CKC is typically assessed during simple, repetitive movements. If this coupling is truly behaviorally relevant, it should generalize to more complex movements. Three studies were conducted on healthy humans to assess how CMC and cortical beta power was related to force fluctuations (P1), the extent to which CKC was related to gross and/or fine motor skills (P2), and to determine whether postural sways were encoded in cortical activity and if this encoding was relevant for postural stability (P3). P1 revealed that transient changes in the power of ~20 Hz activity of the primary sensorimotor cortices preceded (~40 ms) changes in force. The modulations of CMC closely mirrored that of cortical power. In P2, CKC was successfully assessed in a dynamic, upper extremity task and was found to be associated with gross motor skills, but not fine motor skills. The results of P3 showed that a form of CKC with sway dynamics exists while standing upright. Such CKC hinged on both afferent and efferent components and was strongest during complex balance conditions in which the senses were most perturbed. In addition, individuals who were made most unstable by sensory perturbation had the strongest CKC. Collectively, these studies suggest that the interpretation of brain-periphery couplings should be task dependent, with factors like task novelty and complexity being critical for assessing behavioral (dis)advantageousness. As well, our studies revealed that CKC is capable of assessment in complex, multi-jointed tasks and therefore represents a generalizable mechanism of movement encoding. And lastly, the tight mirroring between CKC and cortical beta power modulations suggests that CMC itself is not physiological meaningful beyond that of the role of beta modulations. Brain-periphery couplings, without question, exist in the form of CMC and CKC; however, the extent of their genuine physiological meaning must be carefully questioned in future studies by further exploring the similarity between cortical beta modulations and CMC, and if CKC strength is a trait-like feature that defines movement encoding ability.