One-trial conditioned taste aversion inLymnaea: good and poor performers in long-term memory acquisition

Abstract

In the majority of studies designed to elucidate the causal mechanisms of memory formation, certain members of the experimental cohort, even though subjected to exactly the same conditioning procedures, remember significantly better than others, whereas others show little or no long-term memory (LTM) formation. To begin to address the question of why this phenomenon occurs and thereby help clarify the causal mechanism of LTM formation, we used a conditioned taste aversion (CTA) procedure on individuals of the pond snail Lymnaea stagnalis and analyzed their subsequent behavior. Using sucrose as an appetitive stimulus and KCl as an aversive stimulus, we obtained a constant ratio of 'poor' to 'good' performers for CTA-LTM. We found that approximately 40% of trained snails possessed LTM following a one-trial conditioning procedure. When we examined the timewindow necessary for the memory consolidation, we found that if we cooled snails to 4°C for 30·min within 10·min after the one-trial conditioning, LTM was blocked. However, with delayed cooling (i.e. longer than 10·min), LTM was present. We could further interfere with LTM formation by inducing inhibitory learning (i.e. backward conditioning) after the one-trial conditioning. Finally, we examined whether we could motivate snails to acquire LTM by depriving them of food for 5·days before the onetrial conditioning. Food-deprived snails, however, failed to exhibit LTM following the one-trial conditioning. These results will help us begin to clarify why some individuals are better at learning and forming memory for specific tasks at the neuronal level.

Memory block: A consequence of conflict resolution

“…day 5 snails) Sugai et al, 2007;Mita et al, 2014a,b). However, as shown here, that conclusion was not entirely correct.…”

“…We found in the first cohort (group A, Fig. 1A; N= 20 for each group) that following 20 pairings of the CS and US in the 10 min post-test CS application, the feeding was elicited, indicating that CTA was not observed (Sugai et al, 2007;Mita et al, 2014a,b).…”

“…For example, food deprivation for 1 day results in the best learning and memory. Most interesting to us was the finding that food deprivation for 5 days before training results in little or no learning and memory, possibly because of an overly stressed state (Sugai et al, 2007;Mita et al, 2014a,b).…”

“…day 5 snails) did not exhibit LTM following taste aversion training (Sugai et al, 2007;Mita et al, 2014a,b). One possibility to account for this result is that the CS (a 10 mmol l −1 sucrose solution) used in those studies was more salient in 5-day food-deprived snails than in control snails.…”

Rapid Consolidation to aradishand Protein Synthesis-Dependent Long-Term Memory after Single-Session Appetitive Olfactory Conditioning inDrosophila

“…However, there are some notable exceptions that indicate that spaced training is not always essential to form LTM. In conditioned taste aversion learning in rodents (and pond snails), a single exposure of a tastant, followed by malaise (or salt exposure), leads to a long-lasting avoidance of the associated taste (Garcia et al, 1955;Sugai et al, 2007). Similarly, in the passive avoidance task in chicks, one peck at a bitter-tasting colored bead leads to avoidance of a bead of that color for days (Lossner and Rose, 1983).…”