Olfactory EEG Changes under Serial Discrimination of Odorants by Rabbits

The basic hypothesis in this study is that odor-specific information in the olfactory bulb is carried in the spatial patterns of cooperative activity of masses of bulbar neurons. We predict that the bulbar response to an odorant in any given time frame (on the order of 0.1 sec) is manifested in a spatial pattern of electrical activity over the neurons comprising the bulb (on the order of 100 mm2 in surface area) at a surface grain corresponding to the mean distance between glomeruli (0.25 mm center to center) that spatially coarse-grain the receptor input. Axons from receptors project directly into the bulb and excite second order neurons (the mitral cells) that project in turn to the olfactory cortex. Unit studies of olfactory receptors in several species have shown that cells differ markedly in their sensitivities to odors. Anatomical and electro-physiological studies have shown that there is a degree of topographic order in the axonal connections from the receptors to the bulb (Freeman, 1975). Adrian (1950) predicted that different odorants would cause different spatial activity patterns of receptors in the mucosa, and that their axons would establish different patterns of activity in the spatial array of mitral cells.