Inter trial coherence of low-frequency oscillations in the course of stroke recovery

Abstract

Objective: The aim was to find a sensitive method to highlight the remodeling of the brain's bioelectric activity in post-stroke repair.

Methods: Fifteen mild upper limb paretic stroke patients and age-matched healthy controls were included. Repeated trials of finger tapping around the 10th and 100th days after stroke onset were recorded with a 128-channel EEG. Power spectra and Inter Trial Coherence (ITC) calculations were synchronized to tappings. ITC was correlated with motor performance.

Results: ITC, in low frequency bands, designates the motor related bioelectric activity in channel space in both healthy subjects and patients. Ten days after stroke onset, delta-theta ITC was severely reduced compared to baseline, while three months later ITC reorganized partially over the ipsilesional central-parietal areas reflecting the improvement of motor networks. Decreased ITC in the central-parietal area remained significant compared to controls. Delta band ITC over the dorsolateral-prefrontal cortex correlates with the performance on Nine Hole Peg Test. At post-recovery, non-paretic hand tappings show significantly decreased delta-theta ITC over the supplementary motor area, which reflects network remodeling.

Conclusions: Inter Trial Coherence is a useful measure of brain reorganization during stroke recovery.

Significance: Delta- theta ITC is a sensitive indicator of impaired motor execution.

Keywords: Delta-theta frequencies; EEG; Finger tapping; Inter trial coherence; Post-stroke repair.