An ERP investigation of the Working Memory Stroop effect.

This study aimed to explore the neural activity associated with the Working Memory (WM) Stroop effect. Stroop facilitation and interference effects in WM were also investigated by adding a neutral condition to the WM Stroop paradigm. In each trial, participants were first asked to remember a word in WM, then respond to the color of the subsequent rectangle. The word meaning and rectangular color were congruent, incongruent, or irrelevant (neutral). Finally, a probe word appeared and participants judged whether it was the same as the first presented word. For the color decision task, behavioral results showed that 1) RTs were longer for the incongruent than congruent condition, indicating a WM Stroop effect; 2) RTs were shorter for the congruent than neutral condition, indicating a WM Stroop facilitation effect; and 3) RTs were shorter for the incongruent than neutral condition, indicating no Stroop interference effect in WM. ERPs locked to the rectangle revealed that 1) greater N2 and P3 activity was evoked for the incongruent than congruent condition, indicating more intensive conflict detection and conflict resolution processes for the incongruent condition; and 2) enhanced N2 but decreased P3 components were evoked for the neutral than the congruent and incongruent conditions, indicating a more intensive conflict monitoring process but decreased conflict resolution process for the neutral condition. These results demonstrate that when WM content is congruent with the attention task, it can facilitate attention, but WM content may not interfere with attention when they are incongruent.