Abstract
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. They have been shown to be prokinetic in nature and contain information on various movement parameters. Although high gamma oscillations are widely recognized for their significance in human motor control, their precise function on a cortical level remains elusive. Further, their relevance in human stroke pathophysiology is unknown. Here, we aim to investigate how cortical high gamma oscillations relate to motor performance and motor skill acquisition, and test for possible alterations after ischemic stroke.
We performed an observational study investigating the relationship between cortical high gamma oscillations and motor function. We recorded magnetoencephalography data during a thumb movement speed task in 14 chronic stroke patients (age = 65.4 ± 9.3 years, 7 females), 15 age-matched control participants (age = 64.5 ± 8.4 years, 7 females) and 29 healthy young participants (age = 25.4 ± 4.6 years, 13 females).
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 patients showed reduced cortical high gamma power, surpassing the effect attributable to decreased movement speed in these patients. The decrease of high gamma power, however, did not relate to residual motor function or structural disconnection. In slower movements, we observed distinct high gamma peaks for each movement, whereas in faster movements high gamma activation smeared to fewer distinct peaks. Even though motor skill acquisition was evident in all groups, it was not linked to high gamma power.
Our study is 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. Our findings underscore the potential for exploring non-invasive brain stimulation within the high gamma frequency range to enhance motor rehabilitation after stroke.
Competing Interest Statement
The authors have declared no competing interest.
