The immediate goal of this project is to understand the relationship between temporal spiking patterns in neurons in the olfactory bulb and odorant coding. The long term goal is to relate these finding to information coding in other regions of the brain. The hypothesis to be examined here is that spikes occurring at different times relative to a stimulus pulse are generated by different circuit components and thus carry different information about the stimulus. These experiments are designed to examine how vertebrate olfactory bulb circuits relate to spike patterns of the output mitral and tufted cells (MTs). Two questions will be addressed: 1)Using receptor antagonists as tools, how do NMDA and non-NMDA glutamate receptor inputs contribute differentially to odorant-elicited MT spiking patterns? The hypothesis is that non- NMDA input contributes more than NMDA input to short latency spiking, and thus has a larger effect on burst latency; 2) Do GABAergic inputs contribute differentially to both early and late periods of suppression in MT odorant responses? GABA and a GABA receptor antagonist will be applied during extracellular recording to test the hypothesis that GABAergic inputs contribute to both MT spiking latency and to suppression following spiking. Although, as described below, there have been a number of studies in which pharmacological tools have been used to dissect responses elicited by electrical stimulation, few have used these tools during odor stimulation, and in the vertebrate none have related these response components to the behavioral capabilities of the animal. The projects proposed here will provide new information on this important aspect of the odorant encoding process, and further our knowledge of information processing in sensory systems, in learning and memory, and in the coding and categorization of information during decision making processes. Studies such as these will be critical in understanding brain/behavior relationships.
