A review of the anatomy and function of the white matter tracts in language production and comprehension

Much is known about the role of various cortical areas in language production and comprehension. The shift towards network approaches in recent years has highlighted the importance of uncovering the role of the white matter in connecting these areas. However, despite a relatively large body of research, the function of many of these tracts is still underdefined. In this paper, we present a comprehensive review of the empirical evidence on the role of eight major tracts that are hypothesized to be involved in language processing (inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, the extreme capsule, middle longitudinal fasciculus, superior longitudinal fasciculus, arcuate fasciculus and frontal aslant tract). For each tract, we hypothesize the tract’s role based on the function of the cortical regions it connects. We then evaluate these hypotheses in light of data from three sources: studies in neurotypical individuals, neuropsychological data, and intraoperative stimulation studies. Finally, we summarize the conclusions supported by the data and highlight the areas in need of further investigation.