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 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.

Conceptual representations in the default, control and attention networks are task-dependent and cross-modal

“…In support of this view, Jung-Beeman (2005) summarized evidence that both the left and right hemispheres are engaged in conceptualsemantic cognition, but the right hemisphere seems to perform coarser computations than the left. This view is also corroborated by a recent large-scale fMRI study (n=172) which revealed conceptual effects in both the left and right IPL, but stronger in the left (Kuhnke, Chapman et al, 2022).…”

“…Cross-modal convergence zones integrate modality-specific features into more abstract, cross-modal representations (Binder, 2016;Fernandino et al, 2016a;Kuhnke et al, 2023Kuhnke et al, , 2020bTong et al, 2022). We previously proposed a distinction among cross-modal convergence zones between "multimodal" regions which retain modality-specific information, and "amodal" regions which completely abstract away from modality-specific input (Kuhnke et al, 2023(Kuhnke et al, , 2022(Kuhnke et al, , 2020b. Multimodal regions seem to include the left inferior parietal lobe (IPL) and posterior middle temporal gyrus (pMTG) (Fernandino et al, 2022(Fernandino et al, , 2016aKuhnke et al, 2023Kuhnke et al, , 2020b, whereas the anterior temporal lobe (ATL) acts as an amodal hub of the conceptual system (Jefferies, 2013;Lambon Ralph et al, 2016;Patterson et al, 2007).…”

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 metaanalysis 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, 2022Kuhnke et al, , 2021Kuhnke et al, , 2020bReilly 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, 2022Kuhnke et al, , 2021Kuhnke et al, , 2020bReilly et al, 2016;Seghier, 2013). Alternatively, these multimodal regions may code a knowledge type common to all involved conceptual features.…”