Anyone who has ever suffered a common cold knows that both taste and smell contribute to our experience of food. Understanding how smell and taste interact to ultimately drive food choice will make a major impact on our understanding of disorders that are typically characterized by abnormal food choice, most notably obesity and diabetes. The neural mechanisms underlying taste-smell interactions, however, remain largely unknown, and are the focus of the present proposal. The proposed work follows directly from existing behavioral and neuro- physiological data. Behavioral work has demonstrated an influence of taste on smell in flavor preference for- mation. Recent work from our own lab has identified a potential neural substrate for mediating the influence of taste on smell by demonstrating that primary olfactory cortex (OC) receives gustatory input via primary gustatory cortex (GC). Using rats as a model system, the present proposal will combine naturalistic multisensory stimulus presentation, optogenetics and electrophysiological recordings in the context of a flavor preference learning task to investigate the role of interactions between the primary gustatory and olfactory systems in mediating multi- sensory flavor preference learning.
Specific Aim 1 will use anatomical tracing, optogenetic manipulation of GC neuron axon terminals in OC, and electrophysiological mapping experiments to dissect the systems- and circuit- level organization of gustatory input to OC. Preliminary data suggest the existence of monosynaptic projections from GC to OC.
Specific Aim 2 will then record activity from single OC neurons in response to uni- and multi- sensory flavor stimuli to characterize convergence and integration of flavor-related gustatory and olfactory input. Preliminary data suggest that taste and smell inputs to OC are integrated through functional, spatial and temporal convergence on single OC neurons.
Specific Aim 3 will place the network relaying gustatory input to OC in the context of a taste-mediated flavor preference learning task to determine the causal role GC?OC projections in modulating odor representations and forming flavor preferences. Preliminary data suggest that multisensory ex- perience induces lasting changes in OC odor responses. The results obtained from these experiments will pro- vide novel insight into how OC functions in a natural, behaviorally-relevant multisensory context, specifically uncovering the mechanisms underlying taste-smell interactions in flavor perception and preference formation.
Anyone who has ever suffered a common cold knows that our experience of food depends on both taste and smell. However, we have surprisingly little scientific insight into the mechanisms by which taste and smell interact in flavor perception. Here we apply cutting-edge brain recording and molecular techniques to uncover the mech- anisms by which the brain combines taste and smell during flavor perception and preference formation. The results will help us better understand normal flavor perception, as well as disorders that often result from abnor- mal flavor perception, most notably obesity and diabetes.
