Cortical focus of semantic composition: An fMRI study

Previous research regarding the neural basis of semantic composition has relied heavily on violation paradigms, which often compare implausible sentences that violate world knowledge to plausible sentences that do not violate world knowledge. This comparison is problematic as it may involve extralinguistic operations such as contextual repair and processes that ultimately lead to the rejection of an anomalous sentence, and these processes may not be part of the core language system. Also, it is unclear if violations of world knowledge actually affect the linguistic operations for semantic composition. Here, we compared two types of sentences that were grammatical, plausible, and acceptable and differed only in the number of semantic operations required for comprehension without the confound of implausible sentences. Specifically, we compared complement coercion sentences (the novelist began the book), which require an extra compositional operation to arrive at their meaning, to control sentences (the novelist wrote the book), which do not have this extra compositional operation, and found that the neural response to complement coercion sentences activated Brodmann's area 45 in the left inferior frontal gyrus more than control sentences. Furthermore, the processing of complement coercion recruited different brain regions than more traditional semantic and syntactic violations (the novelist astonished/write the book, respectively), suggesting that coercion processes are a part of the core of the language faculty but do not recruit the wider network of brain regions underlying semantic and syntactic violations.

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Differential contributions of left-hemispheric language regions to basic semantic composition

10.1101/2019.12.11.872457 ◽

2019 ◽

Author(s):

Astrid Graessner ◽

Emiliano Zaccarella ◽

Gesa Hartwigsen

Keyword(s):

Semantic Network ◽

Inferior Frontal Gyrus ◽

Angular Gyrus ◽

Compositional Process ◽

Form Complex ◽

Semantic Composition ◽

Fmri Study ◽

Semantic Dimension ◽

First Time ◽

Basic Semantic

AbstractSemantic composition, i.e. the ability to combine single words to form complex meanings, is a core feature of human language. Despite growing interest in the basis of semantic composition, the neural correlates and the interaction of regions within this network remain a matter of debate. In the present fMRI study, we designed a well controlled two-word paradigm in which phrases only differed along the semantic dimension while keeping syntactic information alike. 33 healthy participants listened to meaningful phrases (“fresh apple”), anomalous phrases (“awake apple”) and pseudoword phrases (“awake gufel”) while performing both an implicit and an explicit semantic task. We identified neural signatures for distinct processes during basic semantic composition: The general phrasal composition process, which is independent of the plausibility of the resulting phrase, engages a wide-spread left hemispheric network comprising both executive semantic control regions as well as general conceptual representation regions. Within this network, the functional connectivity between the left anterior inferior frontal gyrus, the bilateral pre-supplementary motor area and the posterior angular gyrus specifically increases during meaningful phrasal composition. The anterior angular gyrus, on the other hand, guides more specific compositional processing evaluating phrasal plausibility. Overall, our results were stronger in the explicit task, pointing towards partly task-dependent involvement of the regions. Here we provide a separation between distinct nodes of the semantic network, whose functional contributions depend on the type of compositional process under analysis. For the first time, we show that the angular gyrus may be decomposable into two sub-regions during semantic composition.

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