Greg Hickok: UC Irvine Cognitive Sciences & Center for Cognitive Neuroscience

There are two ideas regarding how auditory and motor speech systems interact in language processing. A popular view in the neuroscience community is that motor systems play an important role in the perception of speech. This is an old idea that has been largely (if not completely) abandoned on empirical grounds by the speech science community. However, the discovery of mirror neurons in the macaque brain has resurrected the hypothesis among neuroscientists. The other idea regarding auditory-motor interaction comes out of the motor control literature which has provided compelling evidence that the auditory system plays an important role in speech production. I will review the evidence, current and past, for these two hypotheses and conclude (i) the motor system is not necessary for speech perception, (ii) the motor system may be able to exert a top-down influence on auditory speech perception system but the evidence remains inconclusive and even if real the effects are relatively minor, (iii) there is strong evidence for the reverse relation, that auditory systems play a critical role in aspects of speech production. I will also review a number of fMRI and lesion studies aimed at mapping the cortical circuit supporting sensory-motor interaction in speech processing.