Cortical high gamma power relates to movement speed and is disproportionately reduced after stroke

Motor cortical high-gamma oscillations (60 to 90 Hz) occur at the onset of movement and are spatially focused over the contralateral primary motor cortex. Although high-gamma oscillations are widely recognized for their significance in human motor control, their precise function on a cortical level remains elusive. Importantly, their relevance in human stroke pathophysiology is unknown. Understanding the neurophysiological processes of motor coding could be an important step in improving motor recovery after stroke. We recorded magnetoencephalography data during a thumb movement speed task in 14 chronic stroke survivors, 15 age-matched control participants and 29 healthy young participants. Motor cortical high-gamma oscillations showed a strong relation with movement speed as trials with higher movement speed were associated with greater high-gamma power. Stroke survivors showed reduced cortical high-gamma power, surpassing the effect attributable to decreased movement speed in these participants. Even though motor skill acquisition was evident in all groups, it was not linked to high-gamma power. Our study is, to our knowledge, the first to quantify high-gamma oscillations after stroke, revealing a reduction in movement-related high-gamma power. Moreover, we provide strong evidence for a pivotal role of motor cortical high-gamma oscillations in encoding movement speed.