An ERP investigation of item-scene incongruity at encoding on subsequent recognition.

The aim of the present study was to investigate how item-scene incongruity at encoding influences subsequent item recognition and the associated event-related potential (ERP) old/new effects. Participants (N = 26) studied pictures showing an item in a scene, either in a congruent condition (e.g., a tent in a field) or an incongruent condition (e.g., a shower cabin in a field). Items were presented alone at test. Behavioral data revealed a benefit of incongruent information, with greater source memory performance but no significant effect on old/new recognition judgments. Longer response times for old compared to new items showed that participants not only evaluated the old-new status of objects during recognition, but also worked already on the scene context decision relative to the source memory judgment. An ERP incongruity effect was found at study, with greater N400 amplitude in the incongruent condition than the congruent condition. During recognition, the results provide evidence that item-scene incongruity at study increases the amplitude of ERP old/new effects. A mid-frontal N400 old/new effect was found in the early time window (300-500 ms), and a right frontal sub-component was modulated by item-scene incongruity at encoding. The modulation observed in the later time window (500-800 ms) confirmed previous studies showing that the parietal old/new effect reflects the retrieval of episodic contextual details. The present study shows that the magnitude of ERP old/new effects is sensitive to item-scene incongruity at encoding from the early time window in the right frontal region to the later retrieval processes.