No evidence from MVPA for different processes underlying the N300 and N400 incongruity effects in object-scene processing.
Draschkow D., Heikel E., Võ ML-H., Fiebach CJ., Sassenhagen J.
Attributing meaning to diverse visual input is a core feature of human cognition. Violating environmental expectations (e.g., a toothbrush in the fridge) induces a late event-related negativity of the event-related potential/ERP. This N400 ERP has not only been linked to the semantic processing of language, but also to objects and scenes. Inconsistent object-scene relationships are additionally associated with an earlier negative deflection of the EEG signal between 250 and 350 ms. This N300 is hypothesized to reflect pre-semantic perceptual processes. To investigate whether these two components are truly separable or if the early object-scene integration activity (250-350 ms) shares certain levels of processing with the late neural correlates of meaning processing (350-500 ms), we used time-resolved multivariate pattern analysis (MVPA) where a classifier trained at one time point in a trial (e.g., during the N300 time window) is tested at every other time point (i.e., including the N400 time window). Forty participants were presented with semantic inconsistencies, in which an object was inconsistent with a scene's meaning. Replicating previous findings, our manipulation produced significant N300 and N400 deflections. MVPA revealed above chance decoding performance for classifiers trained during time points of the N300 component and tested during later time points of the N400, and vice versa. This provides no evidence for the activation of two separable neurocognitive processes following the violation of context-dependent predictions in visual scene perception. Our data supports the early appearance of high-level, context-sensitive processes in visual cognition.