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Functional flexibility in language networks
Poster E51 in Poster Session E, Saturday, October 8, 3:15 - 5:00 pm EDT, Millennium Hall
Ileana Quinones1, Manuel Carreiras1,2,3; 1Basque Center on Cognition, Brain and Language, 2IKERBASQUE. Basque Foundation for Science, 48009 Bilbao, Spain, 3University of the Basque Country, UPV/EHU, 48940 Bilbao, Spain
Assessing the synchrony and interplay between distributed neural regions is critical to understanding how language is processed. Here, we investigated the architectural configuration of the language system using a novel multivariate network-based approach, which involved generalized psychophysiological interactions (gPPI toolbox; http://www.nitrc.org/projects/gppi, McLaren and others 2012) and graph-theory measures (i.e., (i.e., strength, clustering, node degree, hubness, betweeness centrality, and modularity). We implemented a sentence comprehension task with native Spanish language speakers, stressing the distinction between syntactic and semantic combinatorial processes. This paradigm manipulates formal – whether the noun-adjective gender relationship was congruent or incongruent – and semantic information – whether the noun refers to an animate (i.e., grammatical gender) or inanimate entity (i.e., conceptual gender) –. Specifically, we explored whether pre-defined ROIs show differential coupling with other brain regions depending on the critical experimental manipulations. Here a multiregional approach previously used by Cocchi and others (2013) was performed. This approach included 24 spherical seed regions that were built in MNI space. Each ROI was defined for each participant as the first eigenvariate of the time series of all active voxels within six mm radius spheres centered on the maximum peak of activation resulting from the group-level effect of the F-test contrast All conditions vs. Null (p<0.05 FWER corrected at the peak level). Given the 24 ROIs included in these analyses, 276 possible connections per subject and condition were generated. Our results demonstrate how the interface between form-based and conceptual features depends on the synergic articulation of brain areas divided into three subnetworks that extend beyond the classical left-lateralized perisylvian fronto-temporal language circuit. Subnetworks 1 and 2 comprised regions previously related with language functions (e.g., IFG, MTG, inferior parietal, supramarginal and angular gyri, and fusiform gyrus). However, subnetwork 3 included areas previously linked with general attentional control mechanisms (e.g., orbitofrontal, superior frontal gyrus, precuneus, and middle and anterior cingulate cortex). Despite this functional segregation, we found clear evidence for interactions between them. We isolated a left parietal cluster showing a significant interaction between gender congruency and gender type. The functional interplay between this cluster and the left perisylvian language-specific circuit proves crucial for constructing coherent and meaningful messages. Importantly, we show that this complex system is functionally malleable: graph features change depending on whether the linguistic input drives access to meaning through form-based or conceptual cues.
Topic Areas: Meaning: Lexical Semantics, Meaning: Combinatorial Semantics