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Sketchpad Series

Cognition in Absentia: An EEG Investigation of Internally Driven Semantic Retrieval

Poster Session E - Monday, March 31, 2025, 2:30 – 4:30 pm EDT, Back Bay Ballroom/Republic Ballroom

Yaqi Xu¹ (yxu293@ucsc.edu), Megan Boudewyn¹; ¹UC Santa Cruz

The N400 is a well-studied neural marker of lexical-semantic processing, but accounts vary as to the specific underlying cognitive processes it reflects. The goal of this study was to test whether N400-like responses are present during lexical-semantic retrieval in the absence of an external stimulus. Participants read highly constraining sentences with sentence-final words in three conditions: expected, unexpected and absent (N=37). An auditory tone accompanied the presentation of every word (including the empty character string in the absent condition) in order encourage participants to anticipate the occurrence of a sentence-final word at a specific time. Preliminary results found that, just as with visually-presented words, sentence-level semantic fit and word frequency of the final words was a significant predictor of amplitude in the absent condition (p<0.05). We plan to use representational similarity analysis (RSA) to further compare the similarities between the three conditions. If our RSA results show a greater similarity between the expected-present and expected-absent conditions than between those conditions and the unexpected condition, it would suggest that the N400 can be used to measure internally-driven semantic retrieval. This pattern of results would also support semantic retrieval accounts of the N400, as an N400-like response should always be present during lexical-semantic retrieval, even in the absence of an external stimulus, if the N400 reflects the relative ease of the retrieval of lexical-semantic information from long-term memory.

Topic Area: LANGUAGE: Semantic