Sign language and the brain

Abstract

Sign languages offer unique insight into the neural basis of language because these languages are visual-manual and do not recruit auditory-vocal processes. Sign languages provide a way to test the constraints on and plasticity of the human language system. This article reviews recent literature on the neural substrates that support the comprehension and production of sign languages. The data clearly show that a left-lateralized fronto-temporal network is reliably engaged during both sign and spoken language processing. However, there are also important differences in the brain networks that support these two language types. The left parietal lobe appears to play a particularly important role in sign language production and comprehension. In particular, parietal cortex may be involved in phonological decoding and encoding (left inferior parietal lobule) and in planning and self-monitoring during sign production (left superior parietal lobule). Overall, investigations of the neurobiology of sign languages reveal both neural invariance and plasticity for language processing.