The overall objective of this research is to understand the role of sensory prediction in the auditory cortex. The ability to predict the sensory consequences of one?s actions plays an important role in shaping sensory coding and guiding behavior. In the auditory system, this prediction is used during vocal production, allowing us to monitor feedback of the sound of our voice. However, the neural mechanisms of this auditory self-monitoring are unknown. This proposal focuses on determining the mechanisms and neural circuits by which sensory prediction changes sensory coding in the auditory cortex during vocalization, and the behavioral role played by such predictions. We approach this using a novel vocal primate model, the marmoset monkey.
Aim 1 focuses on the mechanisms of feedback encoding during vocalization, and tests the hypothesis that sensory prediction shapes auditory cortex responses to calculate an error signal between vocal feedback and the prediction. We record auditory cortex neurons in vocalizing marmosets while adjusting the frequency content of their vocal feedback using frequency shifts of varying direction and magnitude to measure sensitivity to feedback errors. To further investigate potential computational mechanisms by which sensory prediction shapes feedback coding, we measure frequency tuning changes in auditory cortex during vocalization compared to passive listening, and how these relate to predicted vocal acoustics.
Aim 2 investigates the auditory cortical circuits involved in sensory prediction and feedback encoding, testing the hypothesis that the dorsal auditory pathway exhibits greater feedback sensitivity than early auditory cortex. We record responses to altered feedback during vocalization and compare responses between the dorsal ?where and how? pathway with primary auditory cortex (A1) and the ventral ?what? pathway. We further compare the strength of neural activity in predicting compensatory vocal changes during altered feedback. These results have important implications for validating current models of functional specializations within these higher-order auditory pathways.
Aim 3 addresses the behavioral role of sensory prediction in auditory cortex, testing the hypothesis that activity within the auditory cortex is necessary for feedback-dependent vocal control. We combine frequency- shifted vocal feedback with pharmacologic inactivation of auditory cortex to determine if such manipulations disrupt behavioral compensation. We further compare effects of inactivation between hemispheres and sites of different frequency tuning. These experiments will demonstrate a causal role for the auditory cortex in feedback self-monitoring and resulting vocal control.
Our ability to predict the sensory consequences of our actions plays a critical role in our day to day life. In the auditory system, such predictions assist us in listening to the sound of our own voice when we speak, allowing us to quickly correct any errors that we might detect. However, problems with this self-monitoring, for example after hearing loss, can lead to difficulties in speaking properly, and a better understanding of this process will lead to new approaches for hearing, speech, and other communication disorders.