Oscillatory MEG motor activity reflects therapy-related plasticity in stroke patients

Background. A goal of stroke rehabilitation is to harness the capacity of the brain to reorganize following neurological damage and enable restoration of function. Objective. To understand how neural oscillatory motor responses change following a therapeutic intervention and to illuminate whether these neurophysiological alterations correlate with improvements on behavioral measurements. Methods. Magnetoencephalography (MEG) was used to evaluate plasticity in motor networks following 2 weeks of intensive task-oriented therapy, which was paired with sham or peripheral nerve stimulation (PNS). Patients completed unilateral finger tapping before and 3 weeks after therapy as whole-head MEG data were acquired. MEG data were imaged using beamforming, and the resulting event-related synchronizations and desynchronizations (ERSs/ERDs) were subjected to region-of-interest (ROI) analyses. For each ROI, the authors compared the baseline and postintervention MEG response amplitude, volume, and peak location for premovement βERD, movement-onset γERS, and postmovement βERS. Results. Following therapy, all patients showed reduced postmovement βERS response amplitudes in bilateral precentral gyri and reduced γERS amplitudes in the precentral gyrus of the affected hemisphere. This latter response also distinguished treatment groups, as the posttherapy γ reduction was greater in patients who received PNS. Finally, both β and γ response amplitudes were significantly correlated with improvement on several behavioral indices of motor function. Discussion. These case-series data indicate that oscillatory MEG responses may be useful in gauging plasticity in motor cortices following therapy in stroke patients.