Instantaneous EEG coherence analysis during the Stroop task

Objective: In the present study the Stroop effect is analyzed by means of EEG coherence analysis in addition to traditional analysis of behavioral data (reaction time) and ERP analysis. Data from 10 normal subjects are examined. Methods: In particular, a special dynamic approach for a continuous coherence estimation is applied to investigate the procedural evolution of functional cortical relationships during the Stroop task. Results: The frequency band of 13–20 Hz is found to be sensitive to the discrimination between the congruent and the incongruent task conditions on the basis of instantaneous coherence analysis. The magnitude of coherence values within the time interval of late potentials and the maximal coherence values are used to assess the strength of interaction between distinct areas of the cortex. Higher coherences are observed within the left frontal and left parietal areas, as well as between them for the incongruent situation in comparison with the congruent situation. Furthermore, the time-points of maximal coherence allows a procedural discrimination between both situations. The peak synchrony described by the time-points of maximal coherence correlates strongly with the reaction times mainly within the frontal area and between fronto-parietal areas in the incongruent case, whereas this correlation is restricted to the right hemisphere in the congruent case.