Perisylvian language networks of the human brain

Abstract

Early anatomically based models of language consisted of an arcuate tract connecting Broca's speech and Wernicke's comprehension centers; a lesion of the tract resulted in conduction aphasia. However, the heterogeneous clinical presentations of conduction aphasia suggest a greater complexity of perisylvian anatomical connections than allowed for in the classical anatomical model. This article re-explores perisylvian language connectivity using in vivo diffusion tensor magnetic resonance imaging tractography. Diffusion tensor magnetic resonance imaging data from 11 right-handed healthy male subjects were averaged, and the arcuate fasciculus of the left hemisphere reconstructed from this data using an interactive dissection technique. Beyond the classical arcuate pathway connecting Broca's and Wernicke's areas directly, we show a previously undescribed, indirect pathway passing through inferior parietal cortex. The indirect pathway runs parallel and lateral to the classical arcuate fasciculus and is composed of an anterior segment connecting Broca's territory with the inferior parietal lobe and a posterior segment connecting the inferior parietal lobe to Wernicke's territory. This model of two parallel pathways helps explain the diverse clinical presentations of conduction aphasia. The anatomical findings are also relevant to the evolution of language, provide a framework for Lichtheim's symptom-based neurological model of aphasia, and constrain, anatomically, contemporary connectionist accounts of language.

Neural correlates of noncanonical syntactic processing revealed by a picture‐sentence matching task

“…It is thus likely that this activation reflects the syntactic reanalysis required by anomalous sentences or scrambled sentences that were more confusing than the subject-initial sentences used under the AS and PS conditions. A recent intraoperative electrocorticography study in humans showed bidirectional connectivity between the left IFG and the left pSTG/MTG [Matsumoto et al, 2004], and additional evidence for this connectivity has been reported in studies using MRI to investigate structural connectivity [Catani et al, 2005;Friederici et al, 2006]. Therefore, it is possible that this network subserves syntactic integration, thereby combining multiple linguistic information.…”

Dominant hemisphere functional networks compensate for structural connectivity loss to preserve phonological retrieval with aging

“…2005; Friederici 2009). Our DTI protocol was developed for application in healthy adults as well as patient populations alongside fMRI acquisition.…”

Age-related slowing of task switching is associated with decreased integrity of frontoparietal white matter

“…In the regression analyses conducted separately on data from the young and older age groups, the only ROI that showed an RT-FA association in both groups was the left SLF. Results from DTI-based tractography studies suggest that this portion of the SLF originates at or near the supramarginal gyrus (BA 40), occupies the white matter of the pericentral and frontal opercular regions and connects with lateral prefrontal regions including pLIPC (BA 44/6), and DLPFC (BA 46) (Makris et al, 2005;Catani et al, 2005). The notion that switch cost RT is influenced by microstructural properties of WM linking left lateral prefrontal and parietal cortical regions is intriguing because it is in-keeping with previous functional neuroimaging results suggesting that executive control tasks require the coordinated activity of lateral prefrontal and parietal cortical regions (Cabeza and Nyberg, 2000).…”