Non-topographical contrast enhancement in a ten-glomerulus model. A. Odor-evoked spike counts in mitral cells associated with ten different glomeruli exhibiting different affinities for odor ligands, in the absence of contrast enhancement processes. Response profiles for two similar odors are shown (solid and striped bars). For visual clarity, glomerular responses are ordered in this figure according to their affinities for the two model odorants used. B. Mitral cell responses to each of the same two odorants with NTCE processes intact. The addition of intraglomerular inhibition mediated by PG cells and interglomerular inhibition mediated by the ET/SA network strongly disambiguated mitral cell response profiles, abolishing the overlap between the two odorant representations. C. With intraglomerular periglomerular inhibition intact, but in the absence of interglomerular inhibition, mitral cell odorant representations broaden and spike counts rise as stimulus intensity increases. D. The addition of interglomerular feedback inhibition via the ET/SA network normalizes mitral cell activation patterns with respect to odorant concentration, resolving the potential ambiguity between ligand-receptor affinity and ligand concentration. Increased stimulus intensities neither dramatically alter the population of activated mitral cells nor increase spike rates in activated mitral cells. All odor stimuli in this figure were presented for 100 ms.