Odorant category profile selectivity of olfactory cortex neurons.

The olfactory cortex receives converging axonal inputs from many mitral and tufted cells in the olfactory bulb. Recent studies indicate that single cortical neurons integrate signals from diverse odorants. However, there remains a basic question, namely, the signals from which kinds of odorants are integrated by the individual cortical neurons? The present study examined the possibility that some cortical neurons integrate signals from distinct component odorants of natural foods because individual foods produce a fixed combination of odorants. Previous psychophysical studies of core odorants emitted by fruits and vegetables suggest that the olfactory images of individual natural foods are basically characterized by the profile of structural and perceptual categories of food-born odorants. The single-unit spike responses of neurons in the dorsoposterior part of rat anterior piriform cortex to a panel of eight food-related categories of odorants were herein examined. The results showed that many cortical neurons in this region are tuned selectively to either a single category or a specific combination of distinct categories. The cortical neurons showed mixture facilitation and mixture inhibition when stimulated with mixtures of distinct categories, thus suggesting that olfactory circuits may play a role in enhancing the category-profile selectivity of individual neurons. These results indicate that signals from distinct categories of food-born odorants are integrated in these cortical neurons. This suggests that these cortical neurons detect the odorant-category profile of foods to distinguish distinct food odors.