Towards classical and operant approaches to learning, memory and navigation in the wood ant, Formica rufa

In the past century, insects have become models for studying associative learning and memory formation. Learning paradigms have been developed for several insect species and modalities, but they comprise only two main categories: classical and operant conditioning. While the same cues can be learnt in both paradigms, the process by which learning occurs differs on the extent to which animals need to interact with their environment to form a memory. Classical conditioned individuals obtain information about a cue and a reward/punishment passively while operant conditioned animals need perform an action to be rewarded/avoid punishment. Thus, to truly understand how memories are formed and stored in the brain, it becomes essential to identify to which extent self-action within the environment influences learning. Considering this, I have investigated memory formation in wood ants, Formica rufa, through classical conditioning and found that they are able to passively learn the association between a visual cue and a sugar reward. I have explored this paradigm to investigate particularities of this type of learning and showed that these memories can be lateralised, with short- and medium-term visual memories being formed after training with a reinforcement of the right antenna and long-term memories with a reinforcement on the left antenna. Additionally, I have developed a paradigm in which wood ants can walk on an air supported ball in open- or closed-loop with a virtual world. To demonstrate this paradigm is functional, I have investigated the use of self-generated optic flow on the integration of distance, speed and time of walking ants. I found that ants display repeatable walking behaviour that does not require but can be changed by variations of self-induced or external optic flow. This paradigm allows for a fully controlled comparison and analysis of active and passive interactions with a virtual environment on a tethered animal from which neural circuits could be accessible.