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Attentional networks contributions during phonological and semantic judgments revealed by hemispheric lateralization
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Poster D98 in Poster Session D, Wednesday, October 25, 4:45 - 6:30 pm CEST, Espace Vieux-Port
Gaël Jobard1, Ihintza Malharin2, Laure Zago1; 1Groupe d’Imagerie Neurofonctionnelle, Institut des Maladies Neurodégénératives-UMR 5293, CNRS, CEA University of Bordeaux, 2BCBL Basque Center on Cognition, Brain & Language
Functional lateralization in the left hemisphere for language and in the right hemisphere for attention has been extensively studied, but less frequently in the context of verbal tasks. It is important to identify attentional activations during language tasks in order to accurately differentiate language regions from other contributing factors, as attentional involvement can significantly affect the success of language operations. Attention is generally organized into two distinct anatomofunctional networks: a dorsal frontoparietal network (FPN) responsible for voluntary attentional orienting, and a ventral frontotemporal network (FTN) involved in automatic attentional orienting based on external stimuli (Corbetta and Shulman, 2002). A previous study reported that reading activations overlap with right hemisphere attentional regions, suggesting differential engagement of these two networks depending on the type of reading (lexical or sublexical; Ekstrand et al., 2019). In our study, we targeted regions of interest (ROIs) involved in these attentional networks, as identified in an independent functional run, and assessed their activation and lateralization profiles during a phonological and semantic judgment task. In addition to identifying attentional regions based on their lateralization profiles, we aimed to determine if the two networks were differentially engaged depending on the type of language processing. Using slow event-related fMRI, we selected a subset of 125 individuals from the Bil&Gin database (Mazoyer et al., 2016) who exhibited typical left-lateralized language organization (Labache et al., 2020). They first completed a rhyming task (PHONO) where they judged whether visually presented pseudowords had the same ending sound. In the second task (SEM), they identified whether both written words on the screen referred to man-made objects. Our analyses focused on the BOLD signal and lateralization indices in the frontoparietal (FPN) and frontotemporal (FTN) networks identified in the same participants based on task-induced right-lateralized activations and their intrinsic connectivity (Labache et al., 2023). The results revealed significant activation of almost all ROIs in these attentional networks during the language tasks, without showing qualitatively different network involvement based on the task. Generally, PHONO elicited greater and more lateralized activations than SEM in both networks. We observed right lateralizations in certain regions (anterior prefrontal and inferior parietal regions) of the FPN associated with the frontoparietal control system, as well as in regions of the FTN (anterior insula and cingulate cortex) related to the salience network. The lateralizations observed in the FPN were accompanied by contralateral recruitment of the ROIs, indicating inter-hemispheric cooperation or concurrent activity. The rightward lateralizations of the TFN exhibited similar profiles. In contrast, specific regions of the TFN (F3t, STS3, STS4) corresponding to core language areas in the left hemisphere showed left lateralization due to the suppression of homotopic activity in the right hemisphere. This study demonstrated that despite engaging in tasks involving phonological or semantic processing, attentional executive regions that remain right-lateralized can be identified. These regions may play a crucial role in individuals' ability to efficiently engage in and monitor the language processes required by the task. Furthermore, different inter-hemispheric dynamics were observed, with interhemispheric inhibition emerging as a characteristic of language-specific processes.
Topic Areas: Control, Selection, and Executive Processes, Reading