The contribution of surgical brain mapping to the understanding of the anatomo-functional basis of syntax: A critical review

A wide range of studies on language assessment during awake brain surgery is nowadays available. Yet, a consensus on a standardized protocol for intraoperative language mapping is still lacking. More specifically, very limited information is offered about intraoperative assessment of a crucial component of language such as syntax. This review aims at critically analyzing the intraoperative studies investigating the cerebral basis of syntactic processing. A comprehensive query was performed on the literature, returning a total of 18 studies. These papers were analyzed according to two complementary criteria, based on the distinction between morphosyntax and syntax. The first criterion focused on the tasks and stimuli employed intraoperatively. Studies were divided into three different groups: group 1 included those studies that overtly aimed at investigating morphosyntactic processes; group 2 included studies that did not explicitly focus on syntax, yet employed stimuli requiring morphosyntactic processing; and group 3 included studies reporting some generic form of syntactic deficit, although not further investigated. The second criterion focused on the syntactic structures of the sentences assessed intraoperatively, analyzing the canonicity of sentence structure (i.e., canonical versus non-canonical word order). The global picture emerging from our analysis indicates that what was investigated in the intraoperative literature is morphosyntactic processing, rather than pure syntax. The study of the neurobiology of syntax during awake surgery seems thus to be still at an early stage, in need of systematic, linguistically grounded investigations.