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

BackgroundMovement 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. MethodsUsing 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. ResultsUsing 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. ConclusionALS 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.