Functional organization of rat olfactory bulb analysed by the 2-deoxyglucose method.

The spatial patterns of activity elicited in the rat olfactory bulb under different odor conditions have been analysed using the 2-deoxyglucose (2DG) technique. Rats were injected with 14C-2DG, exposed to controlled environments of amyl acetate, camphor, cage air, dimethyl disulfide, and pure air and autoradiographs prepared by the method of Sokoloff. Amyl acetate was associated with regions of glomerular layer densities in the anterolateral and mid- to posteromedial parts of the bulbar circumference, as previously reported. The extents of the densities increased with increasing concentration. Camphor odor was associated with regions of increased density in the anterodorsal and mid- to posteromedial parts of the bulb. Exposure to cage air produced scattered densities in the posteromedial and posterolateral bulb. Exposure to dimethyl disulfide gave variable results. Pure air was associated with a minimal number of small dense foci. The results with amyl acetate, camphor and cage air suggest that patterns for different odors are distinguishably different but overlapping. The regions of activity are greatest in extent and density with the highest odor concentrations. These define the regions within which more restricted and isolated foci appear at lower concentrations. The results thus provide evidence for the specific role of spatial factors in the neural processing of odor quality and odor concentration.