Recording of spontaneous oscillations in the procerebrum of the terrestrial snail Helix during free behavior.

The procerebrum is the central component of the olfactory analyzer in terrestrial snails and slugs; spontaneous rhythmic oscillations have been recorded in this structure, but their role in the mechanisms of odor perception and recognition has yet to be clarified. The present report describes a method for recording total electrical activity from the procerebrum in vivo and demonstrates changes in spontaneous rhythmic oscillations in the procerebrum of the snail Helix in response to olfactory stimulation. Recording of total electrical activity from the snail procerebrum in conditions of free behavior demonstrated a significant reduction in the frequency and an increase in the amplitude of spontaneous oscillations in the procerebrum in the first 10 sec after presentation of the odor of cineole at low concentration, which corresponds to the time required for performance of the olfactory tentacle withdrawal reaction. Presentation of the odor at high concentration resulted in a significant increase in the amplitude of spontaneous oscillations in the procerebrum over the time interval 11-20 sec after odor presentation and a tendency to a decrease in the frequency, which correlates with an increase in the time required for the olfactory tentacle withdrawal reaction. These data suggest an implicit relationship between the amplitude and frequency of oscillations in odor recognition.