The Neurophysiological Impact of Subacute Stroke: Changes in Cortical Oscillations Evoked by Bimanual Finger Movement

Abstract

Introduction: To design more effective interventions, such as neurostimulation, for stroke rehabilitation, there is a need to understand early physiological changes that take place that may be relevant for clinical monitoring. We aimed to study changes in neurophysiology following recent ischemic stroke, both at rest and with motor planning and execution.

Materials and methods: We included 10 poststroke patients, between 7 and 10 days after stroke, and 20 age-matched controls to assess changes in cortical motor output via transcranial magnetic stimulation and in dynamics of oscillations, as recorded using electroencephalography (EEG).

Results: We found significant differences in cortical oscillatory patterns comparing stroke patients with healthy participants, particularly in the beta rhythm during motor planning (p = 0.011) and execution (p = 0.004) of a complex movement with fingers from both hands simultaneously. Discussion. The stroke lesion induced a decrease in event-related desynchronization in patients, in comparison to controls, providing evidence for decreased disinhibition.

Conclusions: After a stroke lesion, the dynamics of cortical oscillations is changed, with an increasing neural beta synchronization in the course of motor preparation and performance of complex bimanual finger tasks. The observed patterns may provide a potential functional measure that could be used to monitor and design interventional approaches in subacute stages.

Figure 1

Schematic representation of the electrode clusters selected for the quantification of visual alpha (a) and mu and beta motor rhythms (b).

Figure 2

Beta power relative to baseline. Both groups showed desynchronization (negative mean power) with bimanual finger opposition. However, stroke patients did not increase beta desynchronization as much as the healthy controls. Significant differences (p < 0.05) are observed between healthy participants and stroke patients in power of the beta rhythm in the premovement and preparation and in the time-locked beginning of bimanual finger opposition. Error bars represent ±1 SE.

Figure 3

Group-averaged time-frequency plots for the motor area (central electrode, Cz), with bimanual thumb opposition task. (a) shows the time-frequency for healthy controls, while in (b), we present data from the stroke patients' group.

Figure 4

Grand-average topographical distribution for the beta rhythm of the control group (a), an example of an individual map from a healthy participant (b), and examples of individual maps for patients with a stroke lesion in the left (c–f) and right (g) hemispheres, during thumb opposition of both hands simultaneously. In each scalp map, red indicates synchronization, while blue is representing the desynchronization.