Despite having such tiny brains, fruit flies can remember pretty well. The brains of these minute animals can store different pieces of information and associations and can recall these for a long time.
A team of scientists in Paris set to find out how such associative memories are "read out" in their brain, as many of the basic principles are the same in both humans and fruit flies.
In their experiments, the neurobiologists conditioned the fruit flies to associate a certain odor with a mild electrical stimulus.
After repeating this classical conditioning experiment only once, the flies had already got the message and turned away from the pertaining odor.
The key in this experiment was that the scientists could temporarily deactivate specific nerve cells.
The responsible nerve cells, known as MB-V2 cells, had to be intact in order for the flies to fully retrieve the associative memory.
The results thus indicated that MB-V2 cells are involved in a memory 'read-out' pathway.
Prior to this experiment, it was known that olfactory information is processed in the lateral horn of the fly's brain.
The neurobiologists' results showed that MB-V2 cells receive information from the mushroom body - a site in the fly brain, where a positive or negative value is given to the odor information - and that they, in turn, relay to the nerve cells in the lateral horn.
Instinctive behavior, such as the avoidance of certain odors, operates directly via the lateral horn and, as such, remains unperturbed by deactivation of the MB-V2 cells," said Hiromu Tanimoto, one of the two leaders of the study.
The study has been published in Nature Neuroscience.