It is not fully understood how spatial and temporal information present in the olfactory system represents the various features of simple odors and combinations of odors. Although the olfactory bulb (OB) has been studied with single microelectrode recordings and various imaging modalities, these techniques are limited in their exploration of potentially complex interactions present in a population of OB neurons. The goals of this proposal are to adapt an existing microelectrode array to investigations in the rat olfactory bulb and to use this structure to probe the fine spatial and temporal features of ensembles of neurons in the output layer of the olfactory bulb under varying stimulus conditions. Microelectrode arrays, simultaneously recording action potentials from a large number of OB neurons in the rat, offer a unique means of investigating the ways ensembles of neurons process olfactory information. The research tasks described in this proposal 1) develop methods for recording spatio-temporal activity in olfactory bulb neurons using the Utah Electrode Array, 2) study the non-linear effects of mixtures of pure odors in these neurons, and 3) correlate psychophysical behavior with electrophysiology for mixtures of various concentrations of pure odors. The training plan emphasizes learning multielectrode electrophysiological techniques, analysis of spatio-temporal ensemble representations of sensory information, histological methods for reconstructing the interface between electrodes and neural tissue, and operant behavior training techniques. This research will open the door for other odor-related research ranging from adaptation and habituation to odortopic maps of the mammalian olfactory bulb which can only benefit by simultaneous multi-electrode electrophysiology. Understanding sensory codes is vital to development of sensory neural prosthesis.