The role of the angular gyrus in semantic cognition: a synthesis of five functional neuroimaging studies

Semantic knowledge is central to human cognition. The angular gyrus (AG) is widely considered a key brain region for semantic cognition. However, the role of the AG in semantic processing is controversial. Key controversies concern response polarity (activation vs. deactivation) and its relation to task difficulty, lateralization (left vs. right AG), and functional-anatomical subdivision (PGa vs. PGp subregions). Here, we combined the fMRI data of five studies on semantic processing (n = 172) and analyzed the response profiles from the same anatomical regions-of-interest for left and right PGa and PGp. We found that the AG was consistently deactivated during non-semantic conditions, whereas response polarity during semantic conditions was inconsistent. However, the AG consistently showed relative response differences between semantic and non-semantic conditions, and between different semantic conditions. A combined analysis across all studies revealed that AG responses could be best explained by separable effects of task difficulty and semantic processing demand. Task difficulty effects were stronger in PGa than PGp, regardless of hemisphere. Semantic effects were stronger in left than right AG, regardless of subregion. These results suggest that the AG is engaged in both domain-general task-difficulty-related processes and domain-specific semantic processes. In semantic processing, we propose that left AG acts as a multimodal convergence zone that binds different semantic features associated with the same concept, enabling efficient access to task-relevant features.

Automated summary

Semantic knowledge plays a central role in human cognition, and the angular gyrus (AG) is believed to be a key brain region for semantic processing. However, the role of the AG in semantic processing is controversial. This study analyzed fMRI data from multiple studies to investigate the response profiles of the AG during semantic processing. The findings suggest that the AG is involved in both general task-difficulty-related processes and specific semantic processes. The left AG acts as a convergence zone, binding different semantic features associated with the same concept to facilitate efficient access to relevant features.