Invertebrate learning and memory

Associative learning is a capacity present in all animals with a nervous system, which allows extracting the logical structure of the world by evaluating the coincidental order of events. It leads to the generation and storage of memories, which can be retrieved in appropriate circumstances to provide adaptive responses to a changing environment. Invertebrates, with their less complex and accessible nervous systems have been pivotal organisms to understand learning and memory at the behavioral, cellular and molecular level. Not only do they exhibit different forms of associative learning, from Pavlovian to operant, from elemental to non-elemental ones, but their memory is also organized following basic principles common to vertebrates. These phenomena could be traced at the circuit and molecular level, thus yielding fundamental insights into the biological basis of learning and memory. Here we will provide an across-species dissection of these capacities focusing on various invertebrate models - from mollusks to insects. We will discuss evolutionary components and extract universal principles underlying learning and memory organization.