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An ERP N400 study: Semantic processing across modalities in the human brain

Abstract
Semantic processing in the brain of both language and action has been associated with the N400; an event-related potential (ERP) that is typically present when information has violated one’s semantic expectations. We know that the brain receives and processes information from multiple modalities which means that cross-modal semantic processing is more aligned with how semantic processing is likely to occur in comparison to unimodal semantic processing. The N400 is a consistent effect across cross-modal language-based studies. But we know that the topographical distribution of the N400 does vary between language-based and non-language-based paradigms. Therefore, to investigate cross-modal semantic processing within the action domain, we presented participants with photographs portraying the implementation of common actions. These sequences concluded with a sound that was either congruent or incongruent with the prior action photographs. In our ERP study of 25 participants, with a mean age of 23 years (SD = 10.78 years), we¹ found an N400 effect for incongruent information processing. In addition, our findings showed a delayed N400 effect and a reduced P200 amplitude for incongruent information. These results suggest that cross-modal semantic processing of action sequences requires an increased cognitive workload which is evidenced when semantic processing does not progress as expected. Considered as a whole, these results indicate that cross-modal semantic processing is similar to unimodal processing. Cross-modal information likely requires the involvement of additional cognitive processes that are not present during unimodal paradigms.
Type
Thesis
Type of thesis
Series
Citation
Date
2023
Publisher
The University of Waikato
Supervisors
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