Cortical lateralization in stroke patients measured by event‑related potentials during motor imagery

Stroke is a leading cause of impairment and disability worldwide, and motor imagery (MI) has been used in stroke rehabilitation. Electroencephalography (EEG) has been used to study MI. However, the characteristic features of EEG during MI in stroke patients have not been established. The purpose of this study was to investigate the difference in event‑related potentials (ERPs) during MI between healthy controls and stroke patients. This study included nine stroke patients and nine healthy age‑matched controls, who performed tasks involving MI, passive movement without MI and passive movement with MI. One hundred and twenty‑eight channel ERPs were recorded to capture cerebral activation. Electrodes E44 and E120 (corresponding to the inferior precentral area) were selected to analyze the lateralization effects of ERPs. Lateralization was calculated as the ratio of the potential at 500 ms at electrode E120 to that at electrode E44. In the controls, the different ERPs exhibited differential direction between the 0‑300 and the 300‑700 ms interval. ERPs were evoked by passive movement with MI and MI alone, but not passive movement without MI. In addition, a lateralization effect in control patients as shown by the observation that the lateralization ratio in passive movement with MI and MI alone was significantly different from that in passive movement without MI (P<0.05). The amplitudes of the different ERPs were significantly smaller in stroke patients compared with those in the controls (P<0.05). The lateralization ratio in the stroke patients was opposite and significantly different from that of the controls (P<0.05). The results suggested that the MI‑induced lateralization effect in ERPs may be used as a measure for evaluating the MI impairment and recovery in stroke patients.