Where Are the Human Speech and Voice Regions, and Do Other Animals Have Anything Like Them?

Abstract

Modern lesion and imaging work in humans has been clarifying which brain regions are involved in the processing of speech and language. Concurrently, some of this work has aimed to bridge the gap to the seemingly incompatible evidence for multiple brain-processing pathways that first accumulated in nonhuman primates. For instance, the idea of a posterior temporal-parietal “Wernicke’s” territory, which is thought to be instrumental for speech comprehension, conflicts with this region of the brain belonging to a spatial “where” pathway. At the same time a posterior speech-comprehension region ignores the anterior temporal lobe and its “what” pathway for evaluating the complex features of sensory input. Recent language models confirm that the posterior or dorsal stream has an important role in human communication, by a reconceptualization of the “where” into a “how-to” pathway with a connection to the motor system for speech comprehension. Others have tried to directly implicate the “what” pathway for speech comprehension, relying on the growing evidence in humans for anterior-temporal involvement in speech and voice processing. Coming full circle, we find that the recent imaging of vocalization and voice preferring regions in nonhuman primates allows us to make direct links to the human imaging data involving the anterior-temporal regions. The authors describe how comparison of the structure and function of the vocal communication system of humans and other animals is clarifying evolutionary relationships and the extent to which different species can model human brain function.