Dr Emiliano Zaccarella | Moving beyond complexity: Neuroanatomical considerations on the linguistic merging mechanism in humans

Language emerges through the continuous combination of words to build phrases and ultimately sentences of potentially infinite length. A prominent hypothesis in theoretical linguistics suggests that the human capacity to build phrasal and sentential structures out of individual words relies on a simple rule-based syntactic computation, commonly known as Merge. In a series of different fMRI datasets, we sought to characterize the neuroanatomical footprint of this computation. We specifically exploited the possible internal subcomponents of Merge—the stringing of elements in inputs; the build up of more complex labeled hierarchies—the recursive nature of its application during the creation of minimally hierarchical phrases and sentences; the functional interface to the semantic system. By linking linguistic descriptive predictions to the hemodynamic profiles obtained from the different studies, we put forward a spatial neural model for Merge, which assigns a peculiar structure-sensitive role to (the most ventral-anterior) BA 44, as the hierarchy-labeling area. Meta-analytical estimation on previous activation patterns for hierarchical linguistic processing conforms to this hypothesis. The deep frontal operculum/anterior-dorsal insula (FOP/adINS), a phylogenetically older and less specialized region, conversely appears to support word-accumulation processing in which the categorical information of the word might be first accessed based on its lexical status, and then maintained on hold before further processing takes place. The differential contribution to semantic processing we found in sub-regions of the anterior IFG, the pSTS and the PC at these early stages of structure formation opens to testable corpus-based functional redefinitions of the semantic hubs within the human linguistic system. Finally, Implications for the ontogenetic emergence of the Merge as developmental pathway towards abstraction, as well as the phylogenetic trajectories linking humans to non-human primates will be introduced.

Poster