Large-scale network involvement in language processing

The human brain's proficiency for language and speech combines a vast reservoir of stored knowledge with flexibility in perceiving and producing subtle nuances of sound. A century ago, Wernicke and Broca discovered regions responsible for fluent and nonfluent aphasia, respectively (Kandel et al., 2000). More recent studies identified additional types of aphasia, such as primary progressive aphasia, with associated lesions in other regions, and non-invasive functional magnetic resonance imaging (fMRI) has identified regions involved in language and speech beyond those highlighted by neurogic pathologies. These regions include parietal cortex, insula, posterior cingulate cortex (PCC), primary sensorimotor cortex, and supplementary motor areas (Binder et al., 2009). As a result of these developments, current views of language representation within the brain, while still centered on classic frontal and temporal Broca's and Wernicke's areas, now encompass much of the cerebral cortex (Patterson et al., 2007).