Caractérisation des mécanismes neurophysiologiques qui sous-tendent la préparation de mouvements avec et sans douleur associée : études en stimulation magnétique transcrânienne et mesures comportementales
|Advisor:||Mercier, Catherine; Bouyer, Laurent|
|Abstract:||Introduction: Motor preparation is a complex process at the interplay between cognitive and motor aspects, during which multiple steps occur and allow to define the parameters of the upcoming movement. When a movement generates pain repeatedly, the central nervous system should eventually be able to anticipate movement-related pain and establish self-protective strategies during motor preparation in order to avoid pain or to minimize its harmful consequences. It has been previously shown that when pain occurs during movement execution, specific changes occur in the muscular activity depending on the role of the agonist/antagonist muscle that protect the painful limb. However, the mechanisms in the origins the effects of pain anticipation during motor preparation remain poorly understood. The main objective of this thesis is to better understand neurophysiological mechanisms that underlie motor preparation with and without associated pain. Methods: A systematic review (study 1) was performed in order to synthetize studies that have investigated motor preparation by measuring changes in reaction time, induced by non-invasive brain stimulation in healthy participants. This offered an opportunity to evaluate the causal contribution of a given cortical region during motor preparation. Then, transcranial magnetic stimulation (TMS) was used in two studies in order to evaluate corticospinal excitability changes in proximal arm muscles during a pre-cued reaching task. In study 2, motor evoked potentials (MEPs) and TMS-evoked movements have been measured in the biceps and the triceps at various time intervals prior to elbow flexion and extension, when executed without pain. This aimed at characterizing corticospinal excitability changes associated with motor preparation. In study 3, nociceptive stimulations were applied during the execution of flexion or extension for two experimental groups and MEPs were measured in the biceps during motor preparation. Behavioral measures (reaction time and peaks of velocity) were also measured to assess the phases of initiation and execution of the movement. Results: Results obtained in study 1 support a functional implication of five cortical regions (dorsolateral prefrontal cortex, posterior parietal cortex, supplementary motor area, dorsal premotor cortex and primary motor cortex), integrated in a fronto-parietal network, in various components of motor preparation ranging from attentional to motor aspects. The results of study 2 reveal an asymmetry in the corticospinal output between flexor and extensor muscles of the elbow as well as differences in the preparation of flexion and elbow extension movements. The results of study 3 show that corticospinal excitability of the biceps is greater before extension (antagonistic context) than before flexion (agonist context) for the direction associated with pain. In addition, participants take longer to initiate the movement associated with pain, but then realize it faster. Conclusion: The results obtained in this thesis have revealed the prominent role of the motor goal on the processes which operate during motor preparation. Indeed, the cortical correlates underlying motor preparation differ according to the type of movement prepared. In addition, corticospinal output for elbow flexor and extensor muscles varies according to the direction of the prepared movement and the stimulation interval during the preparation phase. Finally, pain anticipation affects corticospinal excitability measured during motor preparation. These latest results have also confirmed and extended what the motor control adaptation theory forecast, suggesting the implementation of protective strategies reflected through an increase in the corticospinal excitability of the antagonist muscle and conversely through a decrease of the agonist muscle to the painful movement.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||4 December 2018|
|Collection:||Thèses et mémoires|
All documents in CorpusUL are protected by Copyright Act of Canada.