The relation between thematic role computing and semantic relatedness processing during on-line sentence comprehension.

Xiaoqing Li,Haiyan Zhao,Yong Lu

doi:10.1371/journal.pone.0095834

Abstract

Sentence comprehension involves timely computing different types of relations between its verbs and noun arguments, such as morphosyntactic, semantic, and thematic relations. Here, we used EEG technique to investigate the potential differences in thematic role computing and lexical-semantic relatedness processing during on-line sentence comprehension, and the interaction between these two types of processes. Mandarin Chinese sentences were used as materials. The basic structure of those sentences is “Noun+Verb+‘le’+a two-character word”, with the Noun being the initial argument. The verb disambiguates the initial argument as an agent or a patient. Meanwhile, the initial argument and the verb are highly or lowly semantically related. The ERPs at the verbs revealed that: relative to the agent condition, the patient condition evoked a larger N400 only when the argument and verb were lowly semantically related; however, relative to the high-relatedness condition, the low-relatedness condition elicited a larger N400 regardless of the thematic relation; although both thematic role variation and semantic relatedness variation elicited N400 effects, the N400 effect elicited by the former was broadly distributed and reached maximum over the frontal electrodes, and the N400 effect elicited by the latter had a posterior distribution. In addition, the brain oscillations results showed that, although thematic role variation (patient vs. agent) induced power decreases around the beta frequency band (15–30 Hz), semantic relatedness variation (low-relatedness vs. high-relatedness) induced power increases in the theta frequency band (4–7 Hz). These results suggested that, in the sentence context, thematic role computing is modulated by the semantic relatedness between the verb and its argument; semantic relatedness processing, however, is in some degree independent from the thematic relations. Moreover, our results indicated that, during on-line sentence comprehension, thematic role computing and semantic relatedness processing are mediated by distinct neural systems.

Highlights

Sentence comprehension involves timely computing different types of relations, which include the morphosyntactic, semantic, and thematic relations between its verbs and arguments
Further simple analysis showed that, the Semantic Relatedness effect reached significance both in the agent condition (F1(1,19) = 5.71, p,0.05, MSE = 1163.71; F2(1,40) = 3.78, p = 0.059, MSE = 2336.19) and in the patient condition (F1(1,19) = 25.65, p,0.0001, MSE = 1219.59; F2(1,40) = 15.26, p,0.0001, MSE = 2291.73). Another way of simple analysis revealed that when the Noun and the Verb were lowly semantically related, the reading time in the patient condition was longer than that in the agent condition (F1(1,19) = 10.28, p,0.005, MSE = 689.95; F2(1,40) = 4.15, p, 0.05, MSE = 2021.08); in contrast, when the Noun and the Verb were highly semantically related, there was no significant difference between the agent and patient conditions (F1(1,19) = .21, p = 0.655, MSE = 601.56; F2(1,40) = .03, p = .865, MSE = 2021.08)
Simple-simple analysis found that there was a significant two-way Semantic Relatedness 6 Anteriority interaction over the frontal electrodes (Flateral(1,15) = 5.51, p,.05, MSE = 3.00), but not over the central and parietal electrodes; over the frontal electrodes, the patient condition elicited a larger N400 than the agent condition when the Verb and the Noun were lowly semantically related (Flateral(1,15) = 8.00, p,.05, MSE = 3.24), but not when they were highly semantically related (Flateral(1,15) = .21, p = .654, MSE = 2.10)

Summary

Introduction

Sentence comprehension involves timely computing different types of relations, which include the morphosyntactic, semantic, and thematic relations between its verbs and arguments. This study aimed to examine the interaction between thematic relation processing and lexical-semantic relatedness processing during on-line sentence comprehension, and the potential similarity or differences between these two types of processes. Thematic relations are not equal to the lexical-semantic relatedness that is based on mere shared features or co-occurrence. Both arrest and pilfer are semantically related to thief, thief bears an agent role in the action event defined by pilfer and a patient role in the action event defined by arrest; fireworks and disturb do not co-occur and do not share similar features, but fireworks bears an agent role in the context of someone being disturbed by the fireworks.

Objectives

Results

Conclusion