Resting functional connectivity of language networks: characterization and reproducibility

The neural basis of language comprehension and production has been associated with superior temporal (Wernicke's) and inferior frontal (Broca's) cortical areas, respectively. However, recent resting-state functional connectivity (RSFC) and lesion studies have implicated a more extended network in language processing. Using a large RSFC data set from 970 healthy subjects and seed regions in Broca's and Wernicke's, we recapitulate this extended network that includes not only adjoining prefrontal, temporal and parietal regions but also bilateral caudate and left putamen/globus pallidus and subthalamic nucleus. We also show that the language network has predominance of short-range functional connectivity (except posterior Wernicke's area that exhibited predominant long-range connectivity), which is consistent with reliance on local processing. Predominantly, long-range connectivity was left lateralized (except anterior Wernicke's area that exhibited rightward lateralization). The language network also exhibited anti-correlated activity with auditory (only for Wernicke's area) and visual cortices that suggests integrated sequential activity with regions involved with listening or reading words. Assessment of the intra-subject's reproducibility of this network and its characterization in individuals with language dysfunction is required to determine its potential as a biomarker for language disorders. Molecular Psychiatry (2012) 17, 841-854; doi:10.1038/mp.2011.177; published online 3 January 2012