BEHAVIORAL MODULATION INDUCED BY FOOD ODOR AVERSIVE-CONDITIONING AND ITS INFLUENCE ON THE OLFACTORY RESPONSES OF AN OSCILLATORY BRAIN NETWORK IN THE SLUG LIMAX-MARGINATUS

We compared behaviorally and physiologically the olfactory responses o f slugs (Limax marginatus) that had been subjected to aversive, appeti tive, or unpaired training with food odors (carrot or cucumber). In th e aversive training, the slugs were exposed to the food odor as a cond itioned stimulus (CS), and then quinidine sulfate solution as an uncon ditioned stimulus (UCS) was immediately applied to the lip of the slug s. This training caused a decrease in preference level for the CS. The unpaired training, in which the CS and the UCS were presented to the slugs with a 5-min interval, induced no change in the preference level for the CS. In the appetitive training, the slugs were allowed to eat the CS odor source without UCS application. When we used nonstarved s lugs, it was found that the preference level for the CS increased upon the appetitive training. These results indicate that each training ch anged the preference for the odors in a characteristic manner. In the physiological experiments, we used brain-inferior tentacular nose prep arations isolated from slugs and investigated the olfactory responses of the oscillations in the local field potential (LFP) of the procereb ral (PC) lobe. We found that odor presentation induced various types o f changes in the LFP oscillation frequency, although the rate of occur rence of the frequency modulation differed between odors used in the a versive and the unpaired training (aversive-conditioned and unpaired o dors). The aversive-conditioned odors induced a decrease in the oscill atory frequency. Unpaired odors did not change it. Moreover, odors use d in the appetitive training (appetitive-conditioned odors) induced an increase in the frequency. Thus, it was considered that those modulat ions of PC lobe oscillatory activity were independent of odor and refl ected learned preference for odors.