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Critical brain regions and tracts for syntax acquisition

Poster A55 in Poster Session A, Thursday, October 6, 10:15 am - 12:00 pm EDT, Millennium Hall

Mariacristina Musso¹, Orionas Saprikis¹, Simon Kirsch¹, Volkmar Glauche¹, Cornelius Weiller¹; ¹Uniklinik Freiburg

Introduction: Friederici et al. (2006) reported that novel finite state grammar (FSG) relates to the phylogenetically ventral system centred in the frontal operculum, while phrase structure grammar (PSG) to the phylogenetically younger dorsal system centred in the pars opercularis of Broca’s area. We aimed to investigate if this dissociation could be confirmed in a lesion mapping study in chronic stroke patients. Method: The experiment consisted of three condition-blocks: two tested artificial grammar (AG) acquisition within FSG and PSG, and one tested verbal WM. Correct syllable sequences were generated by FSG or PSG or including at least two of the three target syllables in the WM condition. Incorrect syllables sequence violated the hierarchical dependency of the elements via scrambling or permutation. In the AG conditions, participants performed first a preference classification and, after receiving an implicit-training, a grammatical classification. In the last testing session, the lexicon was changed to test the ability to generalize novel syntactic competence. Support vector regression analysis using the SVRLSMgui package (DeMarco & Turkeltaub, 2018) was used for symptom mapping in 44 left hemispheric stroke patients. Lesion's volume, age, educational age, gender, performance in Corsi, and WM condition were linearly regressed. DTI global tractography from a normative human connectome database was used to visualize the pathways and their cortical termination going through the white matter lesions mapping performance's deficits. Results: As reported in Kirsch et al. (2022), the most relevant predictors for syntax acquisition in each session were grammaticality (grammatical>ungrammatical items) and education. FSG was better than PSG but only within grammatical items in the pre-training sessions, while within ungrammatical items in the post-training sessions. Generalization was possible only in PSG. Worse performance of grammatical preference was localized in the putamen, parieto-temporal cortex, the arcuate fascicle (AF) and capsula-extrema/Unicinatus fascicle (Emc/UF) for grammatical PSG items; in the STG, caudatus and dorsoventral system for grammatical FSG. Worse performance of grammatical classification was localized in the AF for PSG, and in the dorsoventral systems for FSG. More specifically, lesions of STG, Insula, AF, and putamen were associated with poor performance within grammatical PSG; Insula, Putamen, AF, and dorsoventral pathways for grammatical FSG; parietal cortex and Precuneus for ungrammatical PSG; Insula and AF for ungrammatical FSG. Low training contribution (S3>S1) was associated with AF lesion for grammatical PSG; Insula and dorsoventral pathway for grammatical FSG; temporal and dorsal/MDLF pathway for ungrammatical PSG; Insula for ungrammatical FSG. Voxels significantly correlated with generalization’s deficits (S4>S3) were localized in the EmC/UF for grammatical PSG, while in the AF for ungrammatical PSG; in the SMG for ungrammatical FSG. Discussion: Both GT required intact dorsal language-systems to be correctly classified after learning. Lesions of the dorsal/dorsoventral system reduced the ability to learn to classify via implicit feedback. Moreover, the AF lesion was associated with deficits of recognizing ungrammatical items when using a novel lexicon. The ventral system was relevant for the intuitive grammatical preference of both GT. PSG required the integrity of the more extensive ventral system including the UF for grammatical preference and generalization.

Topic Areas: Syntax, Multilingualism