CONSEQUENCES OF FOOD-ATTRACTION CONDITIONING IN HELIX - A BEHAVIORAL AND ELECTROPHYSIOLOGICAL STUDY

Food-attraction conditioning is a learning phenomenon by which adult H elix pomatin acquire the ability to locate food through exposure to th at particular food. Food-conditioned snails can be distinguished from 'naive' snails during their approach to food. 'Naive' snails keep thei r tentacles upright - whereas 'food-conditioned' animals bend the tent acles downward, in a horizontal orientation, pointed in the direction of the food. Tentacle musculature is innervated by two peritentacular nerves (PTn), each projecting to approximately one hemi-section of the tentacle wall. Stimulating the peritentacular nerves caused the tenta cles to bend downward in a manner reflecting the full complement of te ntacle movements performed by conditioned snails. The neural correlate of tentacle movements was investigated in isolated ganglion preparati ons with the posterior tentacles attached. PT nerve activity was recor ded while the olfactory epithelia were stimulated with natural food od ors. Preparations obtained from conditioned animals responded with a s ubstantial increase in unit activity (mean increase 280%) to stimulati on with odor of the conditioned food but not to other odors. Preparati ons from naive animals did not respond to food odor stimulation. The e lectrophysiological results demonstrated that plasticity due to condit ioning the snails in vivo survived dissection and could be monitored i n vitro.