Figure 1

Long-term memory assessment in Junior and Senior animals. A: Long-term memory performance was determined using a single day, multi-trial, non-aversive, appetitive conditioning assay. On day 1, prior to behavioural conditioning animals were tested (“Pre-training test”) by the addition of a disturbance stimulus (DS, pond water), counting the number of rasps for 2 minutes followed by the application of the conditioned stimulus (CS, 4 ppm n-amyl acetate) and counting the number of rasps over the following 2 minutes. Conditioning occurred on day 2 and consisted of pairing the CS with the unconditioned stimulus (UCS; 0.4% sucrose) which was repeated 5 times. A control (unconditioned) group received a similar timed combination of CS and DS. On day 3 animals were subjected to a post-training test protocol identical to the pre-training test conditions. B: Junior and senior animals were randomly assigned to either control or conditioned groups. There was a robust response to conditioning (CS-UCS) in junior animals as displayed by a significant increase in the Δrasp values in the post-training test. In contrast, none of the conditioned senior animals and unconditioned (CS-DS) control junior or senior animals responded with significant feeding movements in the post-training test. These results are indicative of LTM impairment in senior snails. *** = p < 0.001, ns = non-significant.