Functional anatomy of syntactic and semantic processing in language comprehension

TLDR

The study used fMRI to map syntactic and semantic processing onto the brain. Chinese‑English bilinguals performed syntactic and semantic plausibility judgments on verb phrases, using a font‑size judgment task as baseline. The results revealed a large, left‑lateralized network in the left mid‑inferior frontal and mid‑superior temporal cortices that supports both syntactic and semantic processing of Chinese, with stronger left middle frontal activity for syntax and stronger left inferior prefrontal and mid‑superior temporal activity for semantics, and bilinguals applied the same neural systems to English.

Abstract

A functional magnetic resonance imaging (fMRI) study was conducted to map syntactic and semantic processes onto the brain. Chinese-English bilingual subjects performed two experimental tasks: a syntactic plausibility judgment task in which they decided whether a viewed verb phrase was syntactically legal, and a semantic plausibility judgment task in which they decided whether a viewed phrase was semantically acceptable. A font size judgment task was used as baseline. It is found that a large-scale distributed neural network covering the left mid-inferior frontal and mid-superior temporal cortices was responsible for the processing of Chinese phrases. The right homologue areas of these left cortical sites were also active, although the brain activity was obviously left-lateralized. Unlike previous research with monolingual English speakers that showed that distinct brain regions mediate syntactic and semantic processing of English, the cortical sites contributing to syntactic analysis of Chinese phrases coincided with the cortical sites relevant to semantic analysis. Stronger brain activity, however, was seen in the left middle frontal cortex for syntactic processing (relative to semantic processing), whereas for semantic processing stronger cortical activations were shown in the left inferior prefrontal cortex and the left mid-superior temporal gyri. The overall pattern of results indicates that syntactic processing is less independent in reading Chinese. This is attributable to the linguistic nature of the Chinese language that semantics and syntax are not always clearly demarcated. Equally interesting, we discovered that when our bilingual subjects performed syntactic and semantic acceptability judgments of English phrases, they applied the cerebral systems underlying Chinese reading to the processing of English.