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Propagation of the N400 to subsequent words after lexical anomalies depends on the syntactic attachment point
Poster Session E, Sunday, September 14, 11:00 am - 12:30 pm, Field House
Clara Soberats1, Roberto Zamparelli1; 1CIMeC, Università di Trento
The N400 component is widely interpreted as an index of local semantic processing (individual word level), but its role in sentence-level meaning integration remains a subject of major debate (Brouwer & Crocker, 2017; Hagoort, 2019). Moreover, there is growing evidence that Late Positive Component (LPC) is also elicited by the effort to integrate local meaning within the sentence structure (Shen et al., 2016). Here, we present an EEG study designed to test the sensitivity of both components to the syntactic attachment points. The main question we address is whether the N400 or LPC generated by a lexical anomaly propagate to upcoming words in the sentence, and whether such a cascading effect is modulated by constituent structure. We hypothesize that words that follow an anomalous lexical item that remains in the same constituent would elicit either an N400 or an LPC, while equidistant words outside the constituent would not. To this end, we created 200 Italian sentences following a consistent SVO+Modifier structure: [Determiner, Noun, Verb, Determiner, Noun, Preposition, Noun]. Sentences were rendered semantically correct or anomalous by manipulating the semantic congruency between the verb and the object noun. Additionally, half of the prepositional phrases (PPs) were attached to the object noun (Extended-DP condition), the other half to the verb (VP-modifier condition), resulting in four experimental conditions: Correct VP-modifier (“A customer books this table for tomorrow”), Correct Extended-DP (“A rabbit eats various herbs from the garden”), Incoherent VP-modifier (“A customer books this enemy for tomorrow”), and Incoherent Extended-DP (“A rabbit eats various levers of the garden”). We controlled for the semantic distance between the object and the noun within the PP, using cosine similarity on word2vec vectors, and the DP-VP conditions did not show a statistical significant difference (t = 1.012, p= 0.312). Sentences were presented auditorily to 29 native Italian speakers. Cluster-based tests with Monte Carlo permutations revealed a significant (p < 0.05) centroparietal N400 at the object noun and a parietal-occipital LPC when comparing correct to incoherent sentences. LPC extended to all the subsequent words in the anomalous sentences in both Extended-DP and VP-modifier conditions — indicating a propagation independent of the PP attachment point. In contrast, N400 effects at the noun within the PP were observed only in the incoherent Extended-DP condition (“The postman collects many cultures of congratulations”). These findings suggest that, once a lexical anomaly is introduced, semantic integration difficulties cascade across the sentence; however, the N400 appears more sensitive than the LPC to constituent structure and syntactic dependency. References Brouwer, H., & Crocker, M. W. (2017). On the proper treatment of the N400 and P600 in language comprehension. Frontiers in Psychology, 8(AUG), 1–5. Hagoort, P. (2019). The neurobiology of language beyond single-word processing. Science, 366(6461), 55–58. Shen, W., Fiori-Duharcourt, N., & Isel, F. (2016). Functional significance of the semantic P600: Evidence from the event-related brain potential source localization. NeuroReport, 27(7), 548–558.
Topic Areas: Syntax and Combinatorial Semantics, Meaning: Lexical Semantics