The Yerkes-Dodson law and appropriate stimuli for conditioned taste aversion in Lymnaea

Abstract

Abstract The pond snail Lymnaea stagnalis can learn conditioned taste aversion and then consolidate it into long-term memory (LTM). A high voltage electric shock was used as the unconditioned stimulus (US), whereas we previously used KCl. We varied both the strength of the conditioned stimulus (CS) and US to determine if the so-called Yerkes-Dodson law prevailed. This is an empirical relationship between the state of arousal and LTM formation, showing that there is an optimal level of arousal leading to memory formation. However, too little or too much arousal results in poorer LTM. We found here that the most appropriate stimuli to use in taste aversion training in Lymnaea were a 10 mmol l-1 sucrose solution as the CS and a 3-s electric shock as the US.