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The atypical lateralization of language during a reading task is manifested in IFG and STG, but not in the fusiform gyrus
Poster C116 in Poster Session C, Wednesday, October 25, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
María Baena Pérez1, Cristina Cano Melle1, Esteban Villar Rodríguez1, Lidón Marín Marín1, César Ávila1; 1Jaume I University
INTRODUCTION: Studies have consistently reported a strong hemispheric left-lateralization of language, but also that some healthy participants (mostly left-handed) present atypical lateralization of language in the right hemisphere. Lateralization of language is often determined based on the activation in the inferior cortex using verb generation or verbal fluency tasks. However, language consists of multiple cognitive processes like reading, auditory processing, or comprehension, which rely on different functional networks. Here, we employed a simple reading task to investigate the lateralization of language processing in left-handed participants with typical and atypical lateralization of language. Our hypothesis is that individuals with atypical lateralization of language will activate more the reading network in the right hemisphere. METHOD: Ninety-eight left-handed participants were included in this study (53 females, mean age = 23.41 sd = ± 4.68; mean EHI (Edinburgh Handedness Inventory) = 42.34 sd = ±5.25). The laterality of participants was calculated using the verb generation task (Villar-Rodriguez et al., 2020) with the bootstrap method implemented in the LI-toolbox for SPM12 (Wilke & Lidzba, 2007). We categorized our participants as typical (LI > 40) and atypical (LI < 40) based on the activity in the inferior frontal gyrus. No between-group differences were observed in age, sex or EHI. During the reading task, we employed a block design in which participants were asked to read aloud the words presented on the screen (task condition) or say the word “casa” when they saw the "#" symbol (control condition). We determined whole-brain differences in BOLD signal during reading task between typical and atypical groups (voxel-wise p < 0.001; FWE-corrected at p < 0.05). RESULTS: Whole-brain one-sample t-tests (voxel-wise p< 0.001; FWE cluster-corrected at p< 0.05) for typical and atypical participants revealed significant task activations in the Inferior Frontal Gyrus (IFG), Superior Temporal Gyrus (STG), anterior cingulate/SMA and VWFA. The typical > atypical comparison revealed that individuals with a typical lateralization for language showed increased the activation in the left supramarginal gyrus (x=-54 y=-28 z=26; ZE=4.25). The reversed comparison revealed that the atypical group more showed more activation in the right inferior frontal gyrus (x=54 y=17 z=20; ZE= 4.39) compare to the typical group. There were no significant between-group differences in VWFA activation. CONCLUSION: Our results showed a mirrored pattern of activation in the inferior gyrus in participants with atypical dominance for language Also, the typical group had more activation in the left supramarginal gyrus compared to the atypical group. Importantly, our results revealed no between-groups differences in VWFA activation during word reading. Recent studies have shown an association between the development of an atypical lateralization of language and the development of the corpus callosum. Our results are consistent with this view showing mirrored changes only in areas dependent on this tract.
Topic Areas: Reading, Language Production