Vocal communication and the triune brain.

This paper tests the 'fit' between Paul MacLean's triune brain scheme of brain organization and existing knowledge about the pathways mediating vocal communication in mammals. One component of MacLean's limbic system ('paleomammalian brain'), the 'thalamocingulate circuit,' is found to have an important role in expression of vocalizations, particularly the 'isolation call' (such as are given by mammalian infants when distressed or separated from their caregivers). Recent evidence suggests that this circuit may also have a role in perception of infant cries in humans. Outside of this circuit, the triune brain model has little to offer in the way of insights into how the brain is organized to mediate vocal communication. There is little evidence that the striatal complex ('R-complex' or 'protoreptilian formation') is involved in any major way in vocal communication, although it appears to be involved in some visual displays in both reptiles and nonhuman primates. Interestingly, components of the reptilian brain may be involved in human speech production, and avian homologues involved in birdsong. The neocortex ('neomammalian formation') has well-known importance in speech production and perception, but little evidence exists for a role in vocal production in nonhuman mammals. However, cortical mechanisms do play a role in perception of vocalizations, at least in nonhuman primates. It is concluded that a set of neural structures termed the 'communication brain' mediate vocal communication in mammals, and that this model does not fit well into the triune brain scheme of brain organization.