Dysfunctions and Plasticity Mechanisms of Motor System Assessed by Cortico-cortical and Cortico-muscular Coherence Analysis in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized clinically by abnormalities of both upper motor neurons (UMN) and lower motor neurons (LMN). The presence of UMN signs is not always easy to establish. The only technique used in routine to assess the corticospinal dysfunctions is based on transcranial magnetic stimulation (TMS). However, this technique is largely dependent on LMN state and is based on artificial motor cortex activation. The main objective of our study project is to evaluate a new method assessing functional changes in motor system in ALS patients. By using cortico-muscular and cortico-cortical coherences, it could be possible to show modifications in both cortico-muscular relationship and in cortical activity coordination which could be related to clinical state in ALS patients. We notably expect a decrease in cortico-muscular coherence in ALS patients. Furthermore, these analyses could provide new insights in motor system plasticity phenomena. We expect a partial covering of voluntary motor command by cortical areas adjacent to primary motor cortex. Lastly, the hypothesis that an increased proportion of voluntary motor control may be assumed by ipsilateral corticospinal tract could be tested by coherence analyses. Coherence analysis might be a useful method to detect corticospinal tract dysfunctions. This method has the advantage to be painless and not to use artificial stimulations as it is used in TMS.