Axe 3 : Neuro-biomécanique – Biomarqueurs de la motricité saine et altérée / Theme 1

Spinal and supraspinal synchronization mechanisms underlying motor control of muscle activity

This research axis has two main fundamental objectives focused on the study of spinal and supraspinal nervous mechanisms of control of agonist and antagonist muscle activity using wavelet-based coherence analysis in healthy subjects, experts in a sport and patients with impaired motor function.

The first is to contribute to a better understanding of the functional role of cortico-cortical, cortico-muscular and inter-muscular coupling in the regulation of muscle activity, in relation to motor performance. Electrophysiological signals coupling can be viewed as mechanisms that could take part in the maintenance of the neuromuscular performance during voluntary contractions, but their modulation over time remains unexplored. However, the concomitant temporal dynamics of the coupling between each of the cortical, spinal and muscular levels could be a determining factor in the ability of individuals to produce and maintain muscular contraction whatever the environmental conditions. This work follows an interdisciplinary approach with the aim to contribute to the development of a model of muscular activity control in terms of dynamical coupling between the central, spinal and peripheral levels during motor performance.

The second aim is to investigate the contribution of spinal and supraspinal mechanisms to the modulation of cortico-muscular coherence between electroencephalographic and electromyographic signals. Initially considered as a marker of an efferent motor command directly involved in the control of active muscles via the corticospinal tract, cortico-muscular coherence should include the participation of the spinal mechanisms of voluntary contraction. To address this question, this work rely on the study of eccentric contractions caracterized by a specific modulation of muscle neural activation that would depend mainly on pre- and post-synaptic inhibition mechanisms acting at the spinal level. The aim is to compare the evolution of cortico-muscular coherence between isometric, concentric and eccentric contractions for different levels of contraction, and also to study the plasticity of cortico-muscular coherence after sub-maximal eccentric training.

Beyond their fundamental aspects, these projects are inseparable from our clinical research work in brain-injured patients, and are expected to find significant translational implications in a perspective of therapeutic innovation facilitating the recovery of the motor function, in particular concerning the deficit of extension of the upper limb in post-stroke patients.