The neural bases of sentence comprehension: a fMRI examination of syntactic and lexical processing

One of the challenges to functional neuroimaging is to understand how the c omponent processes of reading comprehension emerge from the neural activity in a network of brain regions. In this study, functional magnetic resonanc e imaging (fMRI) was used to examine lexical and syntactic processing in re ading comprehension by independently manipulating the cognitive demand on e ach of the two processes of interest. After establishing a consistency with earlier research showing the involvement of the left perisylvian language areas in both lexical access and syntactic processing, the study produced n ew findings that are surprising in two ways: (i) the lexical and syntactic factors each impact not just individual areas, but they affect the activati on in a network of left-hemisphere areas, suggesting that changing the comp utational load imposed by a given process produces a cascade of effects in a number of collaborating areas; and (ii) the lexical and syntactic factors usually interact in determining the amount of activation in each affected area, suggesting that comprehension processes that operate on different lev els of language may nevertheless draw on a shared infrastructure of cortica l resources. The results suggest that many processes in sentence comprehens ion involve multiple brain regions, and that many brain regions contribute to more than one comprehension process. The implication is that the languag e network consists of brain areas which each have multiple relative special izations and which engage in extensive interarea collaborations.