Taxing working memory with syntax: Bihemispheric modulations

Abstract

Motivated by claims that relegate the syntactic functions of Broca's region to working memory (WM) and not to language-specific mechanisms, we conducted an fMRI and an aphasia study that featured two varieties of intrasentential dependency relations: One was syntactic movement (e.g., Which boy does the girl think [symbol in text] examined Steven?), the other was antecedent-reflexive binding (e.g., Jill thinks the boy examined himself). In both, WM is required to link two nonadjacent positions. Syntactically, they are governed by distinct rule systems. In health, the two dependencies modulated activity in distinct brain regions within the left inferior frontal gyrus and the left middle temporal gyrus. Binding uniquely modulated activation in the right frontal lobe. Receptive abilities in brain damaged patients likewise distinguished among these syntactic types. The results indicate that sentence comprehension is governed by syntactically carved neural chunks and provide hints regarding a language related region in the right hemisphere.