Single-trial learning leads to mid-term memory formation in ants during an appetitive, but not an aversive, task

Insects have been models of associative learning and its underlying memory mechanisms. Research on the fruit fly Drosophila melanogaster and the honeybee Apis mellifera yielded deep insights into the different memory types and their formation dynamics following repeated stimulus exposure. However, less is understood about the ability of insects to learn from a single exposure. Accumulating evidence reveals that several insect species are able to learn from a single trial. Studies have largely focused on odour appetitive learning. In this study, we investigated the ability of the ant Lasius niger to learn from a single trial to associate a reward or a punishment with one side of a Y-maze. The ants successfully demonstrated appetitive learning but no aversive learning. This appetitive learning led to the rapid formation of mid-term memory, remaining sensitive to anaesthesia for at least 15 min post-training. Contrary to single-trial appetitive odour learning described in other species, this learning did not induce the formation of long-term memory, calling for further comparison between learning types.