Wavelet-based estimation of EEG synchronization associated with native and second language processing in Stroop task

ObjectiveTo examine and compare the synchronization of different brain regions during the Chinese and English Stroop tasks.MethodsTen native Chinese speakers with a moderate command of English participated in this study, and event-related potentials were recorded while participants performed the Stroop task. Then wavelet-based estimation of instantaneous EEG coherence was applied to investigate the synchronization of different brain regions during Stroop task.ResultsA greater negativity for the incongruent situation than congruent situation appeared from 350 ms to 600 ms post-stimulus onset over frontal, central, and parietal regions in Chinese Stroop task, while the negativity was absent in English Stroop task. However, not only in Chinese Stroop task but also in English Stroop task was it found significantly higher EEG coherences for the incongruent situation than congruent situation over frontal, parietal, and frontoparietal regions before 400 ms post stimulus onset at β (13–30 Hz) frequency band.ConclusionThis finding indicated that wavelet-based coherence is more exquisite tool to analyze brain electro-physiological signals associated with complex cognitive task than ERP component, and that functional synchronization indexed by EEG coherence is enhanced at the earlier stage while processing the conflicting information for the incongruent stimulus.