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A Language-Specific Left-Lateralized Network for Auditory Naming
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Poster C70 in Poster Session C, Wednesday, October 25, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Also presenting in Lightning Talks C, Wednesday, October 25, 10:00 - 10:15 am CEST, Auditorium
Leyao Yu1, Nikolai Chapochnikov2, Werner Doyle2, Orrin Devinsky2, Adeen Flinker1,2; 1New York University Tandon School of Engineering, 2New York University School of Medicine
Naming is a fundamental cognitive function and is an integral part of language assessment in clinical settings. Recent clinical stimulation mapping and neuroimaging evidence indicate that auditory naming, within the context of everyday linguistic discourse, recruits distinct prefrontal cortex regions compared to picture naming. However, the underlying neural dynamics of these processes remain poorly understood. In this study, we aimed to investigate whether and how auditory naming engages language-specific prefrontal regions to process increasing semantic load. We conducted a battery of language production tasks on 50 neurosurgical patients undergoing Electrocorticographic (ECoG) monitoring. The tasks included picture naming and auditory naming (“what a king wears on his head”), with visual word reading and auditory word repetition serving as control tasks. All tasks utilized the same set of 50 words, but with different retrieval routes (randomly interspersed within the block). Region of interest analysis of high gamma broadband activity (70-150 Hz) revealed sustained enhancement in left inferior frontal gyrus (IFG) and left middle frontal gyrus (MFG) specifically during auditory naming, preceding production. We confirmed the effect with multifactor linear regression model, which showed significant interaction effects of electrodes in the aforementioned regions for auditory and semantic features from -1000 ms ~ 250 ms locked to production, p<0.01. We then employed an unsupervised clustering approach which was data-driven and not constrained to specific anatomical regions. We identified a novel network in the frontal cortex, centered on the border of IFG and MFG, exhibiting robust task-selectivity for auditory naming before articulation, with significantly greater activity across all electrodes and time. Clustering analysis further showed that this network was distinct from another cluster exhibiting pre-articulatory responses irrespective of task within IFG and portions of precentral gyrus. The two networks also exhibit different temporal profiles of activation: the naming network peaks around 450 ms prior to production, and the pre-articulatory network peaks around 250 ms prior to production. To investigate the nature of semantic load in the naming network, we applied three encoding models (acoustic, semantic integration, and task-based attention) across all active electrodes (cross-validated prediction models of high gamma electrode activity). The results provided evidence that the naming network primarily encodes increasing semantic load, rather than acoustic or task-based attention. (r^2 = 0.006 for the semantic integration model after variance partitioning, which was significantly above permutation baseline, p<0.01). Lastly, we investigated the laterality of this network across both hemispheres to assess language-specificity. Our findings demonstrated strong left lateralization within the naming network, while networks associated with sensory perception and motor execution exhibited little significant differences in laterality (95% confidence interval of the activation laterality index for each cluster, varied from -1 to 1 where 1 represents left laterality: motor: [0.0641 0.0665]; auditory: [0.1383 0.1408]; visual: [-0.0016 0.0017]; pre-articulatory: [0.5132 0.5157]; naming: [ 0.6319 0.6339]). In conclusion, our study uncovers a novel left-lateralized naming network centered around the border of IFG and MFG, specifically involved in processing increased semantic load.
Topic Areas: Speech Perception, Language Production