“Simpler nervous systems” are useful experimental base for studying mechanisms of synaptic plasticity at the behavior, cellular and the synaptic levels. Electro-stimulation of viscera of edible snail Helix pomatia was used to appreciate, first, parameters of the stimulation for change of functional state of a snail and, second, to evaluate meaning for a snail (negative or positive) of visceral stimulation in situation of free behavioral choice of self-stimulation. For both tasks twenty of intact snails with implanted paired silver electrodes were used in experiments with recording of movements of animals. At first series thresholds of activation of the snails by local electro-stimulation of viscera were appreciated for stimuli of 50-100 msec. in duration and were about 4—6 V. It was sufficient the single stimulus to activate snail in 48 experiments (from 100, n=100), for others cases it were need two (30 experiments) or three (22 experiments) stimuli. At second series active snails could choose between carrot and a stick that’s movement evoked electrical stimulation of viscera. Time of choice of stick has been compared for condition when snail might electro-stimulate it’s by stick’s and when it cannot, current in back-world system was off. The results were unexpected. Time of preference of stick by snail was three time more in condition of self-stimulation (about 15 min per hour in comparison with 5 min for N=8 and n=94). Obtained data show that visceral electro-stimulation is positive reinforcement for a snail in condition of self-stimulation when activity of the snail changes parameters of the stimulus