Abstract
This study investigates the relation between individual language ability and neural semantic processing abilities. Our aim was to explore whether high-level language ability would correlate to decreased activation in language-specific regions or rather increased activation in supporting language regions during processing of sentences. Moreover, we were interested if observed neural activation patterns are modulated by semantic incongruency similarly to previously observed changes upon syntactic congruency modulation. We investigated 27 healthy adults with a sentence reading task—which tapped language comprehension and inference, and modulated sentence congruency—employing functional magnetic resonance imaging (fMRI). We assessed the relation between neural activation, congruency modulation, and test performance on a high-level language ability assessment with multiple regression analysis. Our results showed increased activation in the left-hemispheric angular gyrus extending to the temporal lobe related to high language ability. This effect was independent of semantic congruency, and no significant relation between language ability and incongruency modulation was observed. Furthermore, there was a significant increase of activation in the inferior frontal gyrus (IFG) bilaterally when the sentences were incongruent, indicating that processing incongruent sentences was more demanding than processing congruent sentences and required increased activation in language regions. The correlation of high-level language ability with increased rather than decreased activation in the left angular gyrus, a region specific for language processing, is opposed to what the neural efficiency hypothesis would predict. We can conclude that no evidence is found for an interaction between semantic congruency related brain activation and high-level language performance, even though the semantic incongruent condition shows to be more demanding and evoking more neural activation.
Highlights
Semantic processing is an integral and important function in humans, necessary for reading, communication, as well as problem solving
In our previous studies on reading in relation to language ability in adults, we found that activation in language-related areas in the right-hemispheric inferior frontal gyrus (IFG) and temporal lobe was related to better language performance when participants were engaged in sentence reading (Van Ettinger-Veenstra et al, 2010, 2012)
We investigated brain activation that was modulated by semantic incongruency by comparing incongruent with congruent sentence reading with a one-sample t-test, using the > contrast
Summary
Semantic processing is an integral and important function in humans, necessary for reading, communication, as well as problem solving. Language processing under extrinsic constraints such as high task demands can both increase and decrease neural activation patterns, depending on the kind of demand that is imposed. Intrinsic constraints such as the cognitive abilities of the participant may result in altered neural patterns. Processing of semantic information is characterized by activation bilaterally in the temporal lobes and the angular gyri (Humphries et al, 2006), and it has been demonstrated that activation in the left inferior frontal gyrus (IFG) is coupled to the integration of sentence information (Hagoort, 2005). An N400 effect emerges mainly from the left temporal lobe when meaningful semantic information is processed. Right-hemispheric activation during semantic tasks is not consistently reported, and may sometimes be related to other processes such as decision making (Gan et al, 2013)
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