Human Arcuate Fasciculus
Language is a human cognitive specialization, and as such, is expected to be supported by human neurological specializations. The arcuate fasciculus is a white matter fiber tract that connects Wernicke’s and Broca’s language areas in the human brain, and also connects the homologues of Wernicke’s and Broca’s areas in non-human primate brains. Damage to the human arcuate fasciculus is implicated in multiple linguistic functions. In contrast to chimpanzees and macaques, the human arcuate fasciculus is larger and extends well beyond classic Wernicke’s area into lateral temporal cortex involved with syntax and semantics. Expansion of this language circuit appears to have displaced adjacent visual pathways in a ventral and posterior direction in the human brain. This specialization of the arcuate fasciculus may help to explain why only humans have language in the complete sense.