In the past few years a series of fundamental-level advances have been made in our understanding of the olfactory system at the receptor level, and at the initial stage of central processing in the olfactory bulb. However, it is probably fair to say that none of the fundamental questions have been answered concerning how the olfactory cortex participates in further processing, despite the existence of a rather detailed 'circuit diagram' for piriform cortex (the largest subdivision of olfactory cortex), and the existence of considerable data on responses to odorants in piriform cortex recorded with a variety of techniques in several species. The comparative lack of progress and interest in olfactory cortex is surprising in view of the relative ease with which this highly laminated system can be studied, the strong arguments for its usefulness as a model to study questions of a general nature concerning cortical function, and the fact that operation of the olfactory bulb clearly cannot be understood in isolation from the cortex in view of the return projection it receives from the cortex that is an order of magnitude heavier than it's output projection to the cortex. The basic rationale for the proposed research program is that, although separate analyses of neuronal circuitry and odor responses in piriform cortex have failed to provide insights into mechanisms of its operation, a carefully designed combination of both approaches will provide a powerful analytical tool.
The specific aims will test a series of predictions from the hypothesis that piriform cortex contains both spatial and ensemble representations of odor quality in different subdivisions, and that the ensemble representation enables powerful analysis, memory, and associative functions via""""""""parallel-distributed"""""""" processes similar to those developed in studies of artificial networks. The experiments will use an integrated approach in which the recording of responses to odorants will be coordinate with anatomical analysis of the connections of single cells and functional groups of cells.
