Behavioral and neural characteristics of adaptive speech motor control

PROJECT SUMMARY/ABSTRACT Sensorimotor learning plays a critical role in the acquisition and refining of all skilled movements, including speech production. From early babbling to fully mature speech articulation, auditory-motor learning reflects central nervous system processes involved in acquiring and updating neural representations of the intricate motor-to-auditory transformations from motor commands to vocal tract movements and speech sound output. Auditory-motor learning is also believed to play an important role in the etiology of developmental speech disorders such as stuttering and childhood apraxia of speech. Over the past two decades, the PI’s laboratory has made important contributions to the field’s understanding of the key mechanisms underlying such speech auditory-motor learning in children and adults. We now propose a novel series of experiments, combining behavioral learning paradigms with a highly innovative neurophysiological approach that allows us to both modulate and record subcortical neural activity. Specifically, we aim to investigate (a) how speech auditory- motor learning can be enhanced and how decay of learning can be minimized, (b) whether feedforward auditory-motor learning also drives updates in feedback control policies, (c) which theoretical insights can be gained from the subset of individuals who are “followers” and paradoxically use a control strategy that leads to increasing auditory error rather than adaptation, and (d) whether, at the neural level, cerebellar and basal ganglia circuits play a distinct role in speech auditory-motor learning versus other forms of speech motor learning. The inclusion of experiments on the neural bases of auditory-motor learning leverages state-of-the-art sensing technology available in very recent Deep Brain Stimulation (DBS) implants with electrodes in either thalamic ventral intermediate nucleus (receiving cerebellar output) or subthalamic nucleus (basal ganglia). Overall, these integrated experiments will elucidate the processes, mechanisms, and neural substrates involved in speech auditory-motor learning. They will also reveal the developmental progression of auditory- motor learning, differences in auditory-motor learning between children and adults, as well as similarities and differences in speech sensorimotor learning vs. limb sensorimotor learning. Furthermore, given that auditory- motor adaptation paradigms cause speakers to implicitly alter their speech output quickly and without effort, this line of work supports the future long-term goal of developing novel, computer-assisted clinical procedures that induce adaptive changes in speech behavior by systematically altering the speaker’s auditory feedback. Thus, the work is directly relevant to public health as the generated knowledge will deepen our understanding of typical speech development, the maintenance of speech articulation skills throughout the lifespan, and fundamental sensorimotor mechanisms underlying developmental speech disorders while simultaneously paving the way for highly innovative clinical techniques for the treatment of a variety of speech disorders.