The Role of the Angular Gyrus in Semantic Cognition – A Synthesis of Five Functional Neuroimaging Studies

Abstract

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 independent effects of both 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 independently 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.

Meta-analytic evidence for a novel hierarchical model of conceptual processing

“…Third, control regions are expected to show stronger activation for harder tasks (Noonan et al, 2013). In contrast, a recent large-scale fMRI study (N = 172) revealed that multimodal IPL shows the opposite relationship: lower activity for harder tasks (Kuhnke et al, 2022). Moreover, left IPL was not engaged in a recent meta-analysis of “semantic control”—the controlled retrieval of conceptual information (Jackson, 2021).…”

“…In contrast to the “amodal” ATL, “multimodal” hubs like left IPL and pMTG retain modality-specific perceptual-motor information about the individual modalities that they bind (Fernandino et al, 2016b; Kuhnke et al, 2022, 2021, 2020b; Reilly et al, 2016b; Seghier, 2013). Hence, these regions are sensitive to modality-specific conceptual information related to several modalities.…”

“…This renders the “amodal” ATL insensitive to modality-specific conceptual content. In contrast, “multimodal” hubs like left IPL and pMTG retain modality-specific perceptual-motor information about the individual modalities that they bind (Fernandino et al, 2016b; Kuhnke et al, 2022, 2021, 2020b; Reilly et al, 2016; Seghier, 2013). Alternatively, these multimodal regions may code a knowledge type common to all involved conceptual features.…”