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

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, where we have previously used KCl. We varied the strength of both the conditioned and unconditioned stimuli to determine whether 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 conditioned stimulus and a 3 s electric shock as the unconditioned stimulus.

Memory block: A consequence of conflict resolution

“…This is referred to as conditioned taste aversion (CTA) (Ito et al, , 2012Kawai et al, 2004;Sugai et al, 2006;Takigami et al, 2014). To produce a CTA, an appetitive stimulus, such as sucrose [the conditioned stimulus (CS)], is repeatedly paired with an aversive stimulus, such as an electric shock [the unconditioned stimulus (US)] Ito et al, 2015). Application of the CS to the lips in naive snails increases the feeding response, whereas application of the US causes snails to withdraw into their shell and terminate feeding.…”

Black tea differs from green tea: it suppresses long-term memory formation inLymnaea

“…learning and memory). Reports in the literature show that BT increases alertness, which based on the Yerkes/Dodson/Hebb curve [12] should result in enhanced LTM formation. We hypothesize that BT will enhance LTM formation.…”

“…LTM was tested 24 h later. For a more detailed description of the procedures used to operantly condition snails see [12–18]. …”

“…We then asked whether if we trained in BT using the typical two 0.5 h training sessions separated by a 1h interval and then testing for LTM 24h later [12–18] would LTM form? Using this procedure GT was shown to enhance or to reverse a blockade of LTM formation [13–15].…”

“…It has been shown that BT has positive effects on cognition [7–9] primarily by enhancing attention. The effects of BT on cognition may also be due to what we call the Yerkes-Dodson/Hebb (Y-D/H) curve effect [12]. The Y-D/H is an inverted-U function and simply stated the Y-D/H curve posits that there is an optimal level of arousal that best suits memory formation.…”