Learning and memory mechanisms in mollusks

Organisms survive by adapting to changes in the external environment, such as light, heat, humidity, and the presence of food. In particular, the presence of food (changes in nutritional status) directly affects life and death, which is known to greatly affect the behavior of the organisms. In many organisms, learning ability is known to improve in the hunger state, but the mechanism is unclear.

To understand this mechanism, freshwater snails (Lymnaea stagnalis) with interesting features on nutritional status and learning ability are used. While many animals are known to change their learning ability in two stages of satiety and hunger, Lymnaea changes its learning ability in three stages: satiety, mild hunger, and strong hunger. In addition, each of the neurons in Lymnaea has its name and their connectivity is well known. Our goal is to determine how nutritional status affects cognitive function from the individual level to the cellular level using Lymnaea stagnalis.
So far, changes in nutritional status have been shown to affect serotonin signaling in the brain, and it is further suggested that insulin signaling is involved in this phenomenon. In the future, we would like to approach the more specific signal cross-talk of serotonin and insulin, and the switching mechanism of learning ability due to the difference in nutritional status.