Abstract
Attributing meaning to diverse visual input is a core feature of human cognition. Typically investigated by violating certain environmental expectations and regularities (e.g., a toothbrush in the fridge), a late event-related negativity (N400) has not only been linked to the semantic processing of language, but also to objects and scenes. Incongruent object-scene relationships are additionally associated with an earlier negative deflection of the EEG signal between 250-350ms – often referred to as N300 – and hypothesized to reflect pre-semantic perceptual processes. We used multivariate pattern analysis (MVPA) to investigate whether these two components are truly separable or if the early object-scene integration activity (250-350ms) shares certain levels of processing with the late neural correlates of meaning processing (400-600ms). Forty participants were presented with semantic inconsistencies, in which an object was incongruent with a scene's meaning. Replicating previous findings, our manipulation produced significant N300 and N400 deflections in a standard ERP analysis. MVPA showed above chance classification of congruent vs. incongruent object-scene relationships during both the N300 and N400 time windows. To test to which degree similar neural patterns occur at different time points -–i.e., if neurocognitive patterns are shared between early and late components –, we used a time-generalized multivariate decoding procedure (King & Dehaene, 2014) 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). This analysis revealed above chance decoding performance for classifier trained during time points of the N300 component and tested during later time points of the N400. Our results show that neural patterns are shared between early and late processing during this complex of distinct ERP peaks – indicating that context processing interacts with early perceptual stages of object processing
Meeting abstract presented at VSS 2018