Converging Evidence for the Neuroanatomic Basis of Combinatorial Semantics in the Angular Gyrus

Abstract

Human thought and language rely on the brain's ability to combine conceptual information. This fundamental process supports the construction of complex concepts from basic constituents. For example, both "jacket" and "plaid" can be represented as individual concepts, but they can also be integrated to form the more complex representation "plaid jacket." Although this process is central to the expression and comprehension of language, little is known about its neural basis. Here we present evidence for a neuroanatomic model of conceptual combination from three experiments. We predicted that the highly integrative region of heteromodal association cortex in the angular gyrus would be critical for conceptual combination, given its anatomic connectivity and its strong association with semantic memory in functional neuroimaging studies. Consistent with this hypothesis, we found that the process of combining concepts to form meaningful representations specifically modulates neural activity in the angular gyrus of healthy adults, independent of the modality of the semantic content integrated. We also found that individual differences in the structure of the angular gyrus in healthy adults are related to variability in behavioral performance on the conceptual combination task. Finally, in a group of patients with neurodegenerative disease, we found that the degree of atrophy in the angular gyrus is specifically related to impaired performance on combinatorial processing. These converging anatomic findings are consistent with a critical role for the angular gyrus in conceptual combination.

Amplification of local changes along the timescale processing hierarchy

“…This hierarchy, as well as the divergence of neural responses observed here, is additionally consistent with previously proposed linguistic hierarchies: low-level regions (A1+) represent phonemes (32,33), syllables (34), and pseudowords (35), while medium-level regions (areas along A1+ to STS) represent sentences (36,37). At the top of the hierarchy, high-level regions (bilateral TPJ, precuneus, and medial prefrontal cortex) can integrate words and sentences into a meaningful, coherent whole narrative (5,15,(38)(39)(40). We found that the regions at the top of the hierarchy had the most divergent response to the two stories.…”

“…It was previously suggested that this network of areas supports multimodal conceptual representation by integrating information from lower level modality-specific areas (11)(12)(13)(14)(15). However, the semantic models used in previous work (9)(10)(11)(12)(13)(14)(15) do not model the relationship between words over time. In real-life situations, the context of words can substantially influence their interpretation, and thereby their representation in the cortex.…”

Components of the Language-Ready Brain

“…It may be the case that effects in these languagerelated regions are due to these processes. Previous research points to a role for the posterior temporal lobe in working memory and cognitive control (Hickok et al, 2003;Glaser et al, 2013) and the angular gyrus in semantic processing (Binder et al, 2009;Price et al, 2015), consistent with this speculation.…”

Origins of the brain networks for advanced mathematics in expert mathematicians

“…S12). Thus, mathematical expertise enables the left angular gyrus, which is engaged in sentence-level semantic integration (35,36), to extend this function to mathematical statements. Importantly, this contribution is only transient, restricted to the sentence comprehension period, because this area was deactivated during mathematical reflection.…”