This project will test a new model of speech motor learning that focuses on plasticity in sensory systems and its effects on speech movements and speech perception. The associated experiments are motivated by the results of our preliminary work and each tests a novel hypothesis related to our new model. The studies in Aim 1 use continuous theta-burst transcranial magnetic stimulation to disrupt activity in auditory and somatosensory cortex following speech motor adaptation to test the hypothesis that these sensory areas of the brain are involved in the consolidation of speech motor memory.
Aim 2 tests the hypothesis that sensory working memory plays a determining role in speech motor learning. If this is the case, then if brain areas in prefrontal cortex that are associated with sensory working memory are suppressed, both learning and working memory should be impaired.
In Aim 3, we test the hypothesis that speech perception is influenced by the repeated pairing of auditory and somatosensory feedback during speech motor learning. If this is the case, then manipulating somatosensory inputs in an experimental model of speech learning, which includes paired somatosensory and auditory signals, should result in subsequent changes to the perceptual classification of speech sounds. Our preliminary work on each of the three aims supports the idea that sensory plasticity plays a key role in speech motor learning and perception, and underscores the need to include these effects in models of speech motor learning. A more complete model of speech motor learning is critical if we are to understand basic mechanisms and develop novel approaches to treatment and rehabilitation for people who are affected by speech motor disorders.
We have designed a series of experiments that test a new model of speech motor learning which focuses on the role in learning of plasticity in sensory systems. A first set of studies uses continuous theta-burst transcranial magnetic stimulation to suppress activity in somatosensory and auditory cortex to test the hypothesis that both are involved in the consolidation of speech motor memory. A second set of studies tests the idea that a sensory region within prefrontal cortex contributes to both sensory working memory and to speech motor adaptation. A final series of studies use an MRI compatible robotic device that delivers speech-like patterns of somatosensory input as participants listen to speech sounds in the scanner. We will use this technique to test the idea that repeated pairing of auditory and somatosensory inputs, as would occur in speech motor learning, serves to engage somatosensory areas of the brain in speech perception.
