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Does the N400 index prediction error? Neurophysiological evidence using the Prediction Potential (PP)

Poster D23 in Poster Session D with Social Hour, Friday, October 7, 5:30 - 7:15 pm EDT, Millennium Hall

Luigi Grisoni1, Rosario Tomasello1,2, Friedemann Pulvermüller1,2,3; 1Freie Universität, 2Humboldt Universität zu Berlin, 3Einstein Center for Neurosciences

The ability to accurately anticipate upcoming words in sentence context is of great importance to process a message easily, quickly, and accurately. Consistently, recent EEG studies have shown a functional neurophysiological correlate of semantic anticipation before words predictable from their sentence contexts (Prediction Potential) and a functional relationship between the prediction potential and post-stimulus (N400, Mismatch Negativity, MMN) responses. We here demonstrate the interplay between pre- and post-word brain responses during sentence comprehension. In particular, sentence fragments that lead one to expect a specific upcoming word elicited large PP responses before the expected target word, whereas such a slow-wave, predictive, response was absent for sentence fragments not associated with strong next-word expectations. That the PP response was related to predictive processing was further demonstrated by significant correlations (across sentences) between the PP and both subjective, and objective (corpus-based) measures of predictability of the upcoming word. Crucially, a negative correlation between the PP and the following N400 response indicated that these two signals are functionally linked. As the N400 increases with smaller PP size, this is consistent with the claim that the N400 is a prediction error response. The main sources underlying the PP and the N400 appeared in inferior prefrontal and posterior temporal regions, respectively; whereas category-specific clusters of activation in posterior, visual, and prefrontal, motor, brain areas for animal- and tool-related nouns, respectively, indicated that both these signals reflected aspects of sentence meaning. Overall, these data reveal that the N400, has a causal antecedent, the PP, which may determine important features of N400 dynamics and topographies.

Topic Areas: Speech Perception, Meaning: Lexical Semantics

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