Choosing appropriate behaviour through learning is important for living well in all animals. Our research interest is to elucidate brain mechanisms for learning and memory with an emphasis on neural circuits. We choose an approach with simple models to this end; Associative memory in the fruit fly Drosophila melanogaster. By conditioning flies with sugar reward or electric shock punishment, the predictive value of an associated sensory cue, such as an odour presented at the same time, becomes positive or negative. The consequence of the formation of appetitive or aversive associative memory is bidirectional behaviour: approach or avoidance to the associated cue, for example. Flies are efficient learners; they can form long-lasting memory through a single associative training session. Our approach is to apply genetic manipulation in a restricted part of the fly brain and to investigate its consequence on behavioural abnormalities. We can precisely control the neural activity of specific target neurons in an non-invasive manner, and therefore manipulate circuit functions in freely moving flies. We also engage in the development of new techniques for behavioral analysis, the application of new genetic tools, and visualization of single cell morphology at a high resolution. Our research has contributed to highlighting the similarity of circuit motifs of memory across animals species. We thus believe that this line of research is one of the most direct approaches toward the cellular basis for the formation, consolidation and recall of memory.