The role of world knowledge in sentence comprehension under working-memory constraints: An fMRI study
Introduction: Comprehension of thematic roles, i.e., "who did what to whom," relies on limited cognitive resources, and constraints on these resources can alter the use of plausibility information derived from world knowledge. Although sentence-processing studies have described how plausibility information constrains interpretation, it remains unclear how this process is supported by the architecture of working memory. This study examines whether the phonological loop, one of the components of working memory, contributes to thematic-role processing based on world knowledge. Methods: Using articulatory suppression and functional magnetic resonance imaging, we examined whether constraining the function of the phonological loop modulates behavioral and neural responses to sentences in which syntactically assigned thematic roles are plausible or implausible given world knowledge. To constrain the phonological loop, we manipulated the task: a single task and a dual task involving concurrent articulation. Results: We found no significant interaction between task and plausibility, although equivalence analyses did not provide evidence for the absence of a plausibility effect during articulation. In contrast, a robust main effect of thematic-role plausibility was observed: implausible sentences elicited greater activation than plausible sentences in the left inferior frontal gyrus (LIFG) and medial superior frontal gyrus (mSFG) at the whole-brain level, and in both the pars triangularis and pars orbitalis of the LIFG in the ROI analyses. Discussion: These findings provide no conclusive evidence that constraining the phonological loop substantially modulates the use of world knowledge in comprehension of thematic roles, while also leaving open the possibility of a smaller task-dependent effect. At the same time, the robust neural responses to implausibility indicate that the LIFG and mSFG consistently contribute to the processing of plausibility information derived from world knowledge.