Distinctive Functionality of Semantic Hubs: Evidence from Semantic Dementia

Semantic cognition relies on a distributed network with multiple candidate hub regions that bind multimodal conceptual information. While the anterior temporal lobe (ATL) is widely regarded as a core semantic hub, the roles of other candidate regions--such as the fusiform gyrus (FFG) and posterior middle temporal gyrus (pMTG)--remain debated, particularly regarding verbal and non-verbal semantic processing within the same sensory modality. This study examined 33 patients with semantic dementia and 20 healthy controls using a comprehensive behavioral battery (word and picture versions of the Pyramid and Palm Trees Test and a word-picture verification task) combined with multimodal neuroimaging, including voxel-based morphometry, diffusion-weighted imaging, and resting-state fMRI. Partial correlation and commonality analyses revealed that (1) the left ATL selectively underpins abstract verbal semantic processing, (2) the left FFG contributes to general semantic processing across verbal and non-verbal stimuli, (3) and the left pMTG plays a critical role in integrating verbal and non-verbal semantic information. White matter tracts linking the left ATL and FFG to the right ATL significantly predicted semantic integration performance, underscoring the importance of inter-hemispheric structural connectivity. Functional measures in contralateral regions, including amplitude of low-frequency fluctuation (ALFF) in the right FFG and degree centrality (DC) in the right pMTG, also predicted integration outcomes, suggesting compensatory network reorganization. These findings highlight functional specialization among semantic hubs and underscore the importance of multimodal, cross-hemispheric approaches for understanding the neural architecture of semantic representation.