Movement-related beta modulation in amyotrophic lateral sclerosis depends on muscle strength: A magnetoencephalography study

Background Movement related cortical beta (13-30 Hz) modulation is fundamental in the preparation and execution of movement. This oscillatory modulation is altered in amyotrophic lateral sclerosis (ALS) during active movement, with reports of both decreased and increased beta band power. These beta band changes have never been examined in a proprioceptive paradigm in ALS. Methods Using magnetoencephalography (MEG) we examined 11 ALS patients and 12 healthy participants. We recorded beta band activity during a session of active movement of the dominant hand index finger, using a visual cue. We also recorded activity during a passive movement of the same finger using a MEG compatible pneumatically activated device. All ALS patients underwent a clinical examination including an estimation of the muscle strength of the arm used for the experiment. Results Using an analysis of variance (ANOVA), we find that movement related beta band power is modified by ALS and the amplitude of beta power is decreased, both for the active and passive movements. We also find that the beta band power modulation depends on the muscle strength of the arm used, with movement related power amplitude being decrease in patients with arm weakness. This was observed for both active and passive movement. Conclusion ALS patients show decreased movement related beta band amplitude compared to the healthy control group. The decrease seems to depend on disease severity. These results show that ALS affects the motor outputs and sensory inputs of the sensorimotor cortex and that the modulation differs depending on disease severity. Severity dependent modulation of beta power could be related to disturbance in excitatory/inhibitory intracortical circuitry. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by by the Innovation Fund Denmark with a grant for the REMAP project (Grand Solutions, Grant No. 6153-00010B). As well as by the Department of Clinical Medicine at Aarhus University. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The scientific ethic committee of Region Midtjylland, Denmark gave ethicak approval for this work. (ID number: 65059) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors, as long as they can be considerd within the GDPR data protection framework.