Lecture given on August 30th 2018 by William Matchin, Ph.D., at the University of South Carolina in the C-STAR lecture series.

Dr. Matchin is an Assistant Professor of Communication Sciences and Disorders at the University of South Carolina.

Abstract:
Syntax, the hierarchical structure of sentences, enables humans to express an infinite range of meanings through finite means. As such, the neurobiology of syntax has been intensely studied, with a primary focus on the inferior frontal gyrus (IFG), but with little convergence of evidence or consensus of ideas. We propose a novel, neural framework for syntax that integrates research in linguistics, psycholinguistics, and neuroscience. The key region is the posterior middle temporal gyrus (pMTG), coding syntactic word frames which enable the computation of combinatorial meaning via its connectivity with an anterior entity semantic system and a posterior event semantic system. Unlike other proposals, there is strong convergence of evidence on the pMTG as a syntactic hub: (i) it reliably activates for sentence structure independently of semantic content, (ii) does so regardless of the sensory-motor modality of expression (sound, orthography, and sign language) and (iii) damage to the pMTG impairs sentence comprehension as well as judgments of syntactic well-formedness. Further, the pMTG is optimally located at the nexus of phonological and semantic networks with which is must interface. Finally, we argue that the pMTG syntactic hub participates in both comprehension and production while the non-hierarchical morphosyntactic function of the IFG is primarily tied to production, illustrating this asymmetry through grammatical deficits in fluent aphasia.