Hierarchical processing in language and non-language domains

Abstract

Language processing is a trait of human species. The knowledge about its neurobiological basis has been increased considerably over the past decades. In patient studies, various lesions have been known to be related to specific language deficits. In the studies with healthy controls, different brain regions in the left hemisphere have been identified to support particular language functions. In this talk, I will focus on the process characterized by hierarchical and recursive structures and discuss its neural underpinnings in various domains including language. The processing of hierarchically complex sentences is known to recruit Broca’s area. Interestingly, comparisons between language hierarchy and complex hierarchical structures that mimic those of natural languages suggest functional segregation of the prefrontal cortex (PFC) determined by two principals: one is a cognitive hierarchy for which cascade of information is represented with a posterior–to–anterior gradient pattern of activations and the other is a degree of automaticity which is confined to the posterior parts of the PFC (Broca’s area) processing complex syntactic hierarchies in natural language. Moreover, this functional specificity of the PFC has been observed in subcortical structures such as caudate nucleus or thalamus substantiated by parallel fascicles showing a high correspondence between functional mapping and structural connectivity.