The ability to improve our perceptual skills- to get better with practice- is critical for the acquisition of many complex behaviors, including speech and language. Despite its importance, our understanding of the neural mechanisms underlying this process, known as perceptual learning, remains limited. Recent evidence suggests that training-based plasticity occurs in the top-down networks that modulate auditory cortical activity during task engagement, likely playing an important role in generating long-term improvements in sound encoding and perception. The goal of this project is to explore this hypothesis, specifically focusing on one candidate brain region- the orbitofrontal cortex (OFC). First, to establish the anatomical substrate of this modulation, direct and indirect pathways from OFC to ACx will be characterized in Mongolian gerbils (Meriones unguiculatus) using anatomical tract tracing. Second, to determine the temporal dynamics of top- down activity during perceptual learning, multichannel extracellular recordings will be acquired wirelessly from OFC as animals train and improve on an auditory detection task. Third, to determine whether OFC-mediated modulation of auditory cortical activity plays a causal role in perceptual learning, optogenetics will be used to manipulate OFC activity while simultaneously monitoring auditory cortical response properties and behavioral output. This line of inquiry is well positioned to answer fundamental questions in the fields of auditory learning and memory, and holds the potential to inform the development of clinical treatments to improve perceptual skills in patients with hearing, speech, or language deficits.
The neural mechanisms supporting auditory perceptual learning are largely unknown. The current project addresses this issue by examining the role of one specific brain region, orbitofrontal cortex, in this process. Findings from this proposal may one day lead to the development of training or treatment regimens to facilitate language learning and musical training in both normal-hearing and hearing-impaired listeners.