Broca's and Wernicke's Areas

It has been suggested that Broca’s and Wernicke’s areas are unique to humans. Broca’s and Wernicke’s areas are cortical areas specialized for production and comprehension, respectively, of human language. Broca’s area is found in the left inferior frontal gyrus and Wernicke’s area is located in the left posterior superior temporal gyrus. Non-human primates (both apes and monkeys) possess cortical areas that are in similar locations to and have similar cytoarchitecture as Wernicke’s and Broca’s areas in humans, and are probably homologous to them. The putative macaque homologue of Broca’s area, known as area 44 or area F5, shares functional properties with human Broca’s area. In both species, the region represents non-linguistic hand and mouth movements. Evidence also suggests that both species may have mirror neurons in this region that are involved in understanding the actions and intentions of others. In both macaques and humans, this region is likely involved in producing orofacial expressions and in understanding the intentions behind orofacial expressions of others. In humans, it has evolved an additional communicative function, namely speech production. However, it does not appear to be involved in monkey vocalizations, which are instead mediated by limbic and brainstem areas. Regarding Wernicke’s area, evidence suggests that the left superior temporal gyrus is specialized for processing species-specific calls in macaques just as it is specialized for speech comprehension in humans, although the specific anatomical focus of this macaque specialization is still in doubt. Despite substantial anatomical and functional similarity between Wernicke’s and Broca’s areas in humans and their homologues in non-human primates, there are noteworthy differences in connectivity between the two regions, with humans possessing markedly stronger and more widespread connectivity via the arcuate fasciculus pathway. In fact, tract tracing studies suggest that the dominant projection of the macaque homologue of Wernicke’s area is to dorsal prefrontal cortex rather than to Broca’s area homologue.