What do we have in common with the common fruit file? If you guessed dopamine reward neurons, you are correct! An international team of neurobiologists and imaging scientists led by Hiromu Tanimot, from the Max Planck Institute for Neurobiology in Martinsried, found that in the fruit fly's brain responses to sweet odors depend on specific groups of neurons and neural circuits. Their work was published online on July 18 in the journal Nature, and provides a glimpse on the cellular mechanisms involved in reward processing in the fly brain, which until now, were unknown.
The researchers found that memories of smells associated to sweets lead to the development of food-seeking behaviors toward such smells. Likewise, memory is also involved in reinforcement of negative stimuli, such as high temperature. It turns out that a group of neurons that respond to the neurotransmitter dopamine are involved in both negative and positive signaling. The associations between both types of stimuli and the memories enable the flies to develop conditioned behaviors upon perception of either negative or positive odors. Using genetic mutant flies and advanced "In vivo" calcium imaging, researchers were able to identify the specific cells responsible for reward processing, and the independent local circuits in the midbrain responsible for associating either positive or aversive behaviors. Their work will help future research aimed at understanding the cellular basis of reward and punishment signaling in the brain.