Thesis Defense - Matthew Mosso

Title: A subtype of somatostatin inhibitory neuron reflects predictive stimulus-reward relationships during sensory association learning Abstract: Inhibitory interneurons in primary sensory cortex play a key role in shaping activity during sensation, perception, and cognition. Somatostatin (SST) expressing inhibitory neurons are a subclass of inhibitory neuron that seem to play a critical role in enabling cortical reorganization of excitatory networks during learning. However, functional responses to sensory stimuli, as well as their anatomical, electrophysiological, and molecular phenotypes are heterogeneous. Whether considering distinct subtypes of SST neurons demarcated by molecular expression profile is helpful toward explaining variability in activity and plasticity during learning is not yet well understood. In this study, we leverage confocal and 2-photon imaging to measure functional and anatomical plasticity in SST neurons residing in layer 2/3 of primary somatosensory cortex while mice learn a stimulus reward association and probe whether SST neurons expressing Calb2 are targeted for plasticity. We found that excitatory synaptic size and activity in SST-Calb2 neurons was reduced during learning. Furthermore, we found that these neurons were not suppressed when stimuli were not predictive of reward outcome. This may indicate that SST-Calb2 neurons participate in a circuit within primary somatosensory cortex that reflects the predictive value of a stimulus. Committee: Dr. Alison Barth (Advisor) Dr. Eric Yttri (Chair) Dr. Kate Hong Dr. Caroline Runyan, University of Pittsburgh