Localization, Diversity, and Behavioral Expression of Associative Engrams in Drosophila ☆

New techniques and resources for remote control of neuronal activity at single-cell resolution have led to an explosion of research into the behavioral neurogenetics of the memory trace (engram) in the fruit fly Drosophila . The available data suggest that after odor-punishment training, associative and odor-specific engrams are local to a single layer of processing along the olfactory pathway, the presynaptic output terminals of the mushroom body Kenyon cells. At the same time, engrams are distributed across this layer for different mnemonic aspects of such a training event, and for different kinds of training event. This nature of engrams as being local and distributed can be revealed at due resolution in Drosophila – as can the way learned behavior is organized in an outcome-oriented way.