Evaluating the arcuate fasciculus with combined diffusion-weighted MRI tractography and electrocorticography

Abstract

The conventional model of language‐related brain structure describing the arcuate fasciculus as a key white matter tract providing a direct connection between Wernicke's region and Broca's area has been called into question. Specifically, the inferior precentral gyrus, possessing both primary motor (Brodmann Area [BA] 4) and premotor cortex (BA 6), has been identified as a potential alternative termination. The authors initially localized cortical sites involved in language using measurement of event‐related gamma‐activity on electrocorticography (ECoG). The authors then determined whether language‐related sites of the temporal lobe were connected, via white matter structures, to the inferior frontal gyrus more tightly than to the precentral gyrus. The authors found that language‐related sites of the temporal lobe were far more likely to be directly connected to the inferior precentral gyrus through the arcuate fasciculus. Furthermore, tractography was a significant predictor of frontal language‐related ECoG findings. Analysis of an interaction between anatomy and tractography in this model revealed tractrography to have the highest predictive value for language‐related ECoG findings of the precentral gyrus. This study failed to support the conventional model of language‐related brain structure. More feasible models should include the inferior precentral gyrus as a termination of the arcuate fasciculus. The exact functional significance of direct connectivity between temporal language‐related sites and the precentral gyrus requires further study. Hum Brain Mapp 35:2333–2347, 2014.