The Primate Frontal and Temporal Lobes and Their Role in Multisensory Vocal Communication

By exploring how existing primates use their vocalizations, numerous investigators are building a rigorous, testable framework for how speech might have evolved. Some have suggested that the ability to develop/evolve language depends on the ability to form multisensory associations, and imply that this ability is unique to humans. If its multisensory nature is a fundamental feature of human speech, whereby visual/facial and vocal signals are inextricably linked, then how did such a mechanism evolve? This chapter explores this issue by presenting (1) behavioral evidence that nonhuman primates integrate face and voice information; (2) anatomical evidence that the temporal and frontal cortices of primates are reciprocally connected and are part of a circuit that subserves the integration of face and vocal signals; and (3) physiological evidence that cortical areas in the temporal and frontal lobes of primates show integrative responses to combined face/voice stimuli.