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Prior research on the neural bases of syntactic comprehension suggests that activation in the left inferior frontal gyrus (lIFG) correlates with the processing of word order variations. However, there are inconsistencies with respect to the specific subregion within the IFG that is implicated by these findings: the pars opercularis or the pars triangularis. Here, we examined the hypothesis that the dissociation between pars opercularis and pars triangularis activation may reflect functional differences between clause-medial and clause-initial word order permutations, respectively. To this end, we directly compared clause-medial and clause-initial object-before-subject orders in German in a within-participants, event-related fMRI design. Our results showed increased activation for object-initial sentences in a bilateral network of frontal, temporal and subcortical regions. Within the lIFG, posterior and inferior subregions showed only a main effect of word order, whereas more anterior and superior subregions showed effects of word order and sentence type, with higher activation for sentences with an argument in the clause-initial position. These findings are interpreted as evidence for a functional gradation of sequence processing within the left IFG: posterior subportions correlate with argument prominence-based (local) aspects of sequencing, while anterior subportions correlate with aboutness-based aspects of sequencing, which are crucial in linking the current sentence to the wider discourse. This proposal appears compatible with more general hypotheses about information processing gradients in prefrontal cortex (Koechlin & Summerfield, 2007).Copyright © 2012 by Elsevier Inc. [ABSTRACT FROM AUTHOR]

It has often been suggested that the role of Broca's region in sentence comprehension can be explained with reference to general cognitive mechanisms (e.g. working memory, cognitive control). However, the (language-related) basis for such proposals is often restricted to findings on English. Here, we argue that an extension of the database to other languages can shed new light on the types of mechanisms that an adequate account of Broca's region should be equipped to deal with. This becomes most readily apparent in the domain of word order variations, which we examined in German verb-final sentences using event-related fMRI. Our results showed that activation in the pars opercularis - a core subregion of Broca's area - was not only modulated by the relative ordering of subject and object, but also by a further factor known to affect word order in a number of languages, namely referentiality. Notably, the finding provides the first demonstration of a word order-related activation difference within subject-initial sentences in this region. Additional parametric analyses using individual behavioral data as predictors further attest to the independence of the pars opercularis activation from: (a) sentence acceptability, and (b) difficulty in performing the experimental (judgment) task. We argue that these and related findings attest to the need for a processing mechanism that can manipulate predicate-independent, interacting and hierarchically structured relational representations during real time comprehension. These properties pose a challenge to existing accounts of pars opercularis function.Copyright © 2009 by Elsevier Inc. [ABSTRACT FROM AUTHOR]