A central issue in sensory research is understanding how behaviorally relevant stimuli are represented in the activity of neural networks. In this proposal, we explore the links between the function of neuronal circuits and behavior in the olfactory system. When animals encounter a novel odorant or environment they quickly transition from passive respiration to active sniffing. In humans, impaired sniffing in Parkinson's patients leads to olfactory task deficits. Although sniffing is proposed to play an important role in the formation of olfactory percepts, it is not known how cortical networks process information acquired during sniffing. The experiments we describe in this proposal investigate the cellular and circuit-level mechanisms that produce dynamic cortical response patterns that are reflective of input obtained during passive respiration versus active sniffing. Our preliminary data suggests that short-term synaptic plasticity in olfactory bulb inputs and local interneuron microcircuits act synergistically to produce differential cortical population responses during passive respiration versus active sniffing. We will use a combination of in vitro calcium imaging and simultaneous, multi-neuron, electrophysiological recording to elucidate the roles of synaptic plasticity and circuit architecture in shaping cortical responses. Such a mechanistic and detailed analysis olfactory cortical circuitry will provide an important framework for understanding how olfactory information is processed during passive and active behavioral states. PUBLIC HEALTH RELEVANCE: Despite years of research, and considerable progress in understanding how the brain represents sensory information, direct links between sensory input, neural activity and behavior remain elusive. Sniffing is a well-known behavior in humans and animals and a single sniff provides a snapshot of the olfactory world. Impaired sniffing due to disease can result in olfactory perceptual deficits. The experiments in this proposal investigate the microcircuit mechanisms by which behaviorally relevant patterns of olfactory input during sniffing are reflected in the spatiotemporal patterns of cortical neural activity. Such studies are critical for understanding how sensory input is transformed during cortical processing to form salient percepts and behavioral responses.