The researchers said that in flies just 12 brain cells were responsible for what is known as "associative learning". They modified these neurons by adding receptors for ATP, so that the cells activate in the presence of the chemical, but since ATP isn't usually found floating around a fly's brain, the flies generally behave just like any other fly. Most interestingly, however, is that the scientists then, injected ATP into the flies' brains, in a form that was locked inside a light-sensitive chemical cage. When they shined a laser on the fly brains, the ATP was released, and the "associative learning" cells were activated. The laser flash was paired with an odor, effectively giving the fly a memory of a bad experience with that odor that it never actually had, such that it then avoided that odor in later experiments.
This research, says Professor Gero Miesenböck, the lead investigator of the study, has begun to unravel how animals and humans learn from mistakes and how "error signals" drive animals to adapt their behavior.
They describe their findings in the journal Cell.