New research by Janelia scientists and collaborators at the University of North Carolina at Chapel Hill shows how a cluster of neurons in the fruit fly brain transforms memories about past rewards into actions, helping the fly navigate to find food.

Like other insects, flies turn into the wind, or upwind, to locate the source of attractive odors. The fly’s olfactory system detects and senses odors carried by the wind, guiding the fly to the reward.

New research identifies neurons in the fly brain that control upwind steering. When the neurons are activated (red box), the flies turn toward the wind and walk upwind. Credit: Aso et al.

In the fly, a brain region called the mushroom body processes and integrates olfactory information. Multiple compartments in the mushroom body act in parallel to assign positive or negative values to an odor stimulus, but how these signals are translated into motor actions is unknown.  

The new research shows reward memories formed in different compartments of the mushroom body elicit distinct behaviors, with only some driving the fly’s upwind movement. The study identifies a cluster of neurons – Upwind Neurons or UpWiNs – that integrate inhibitory and excitatory inputs from these compartments, causing the fly to turn and move into the wind.  

Overlay of mushroom body output neurons MBON-α1 and MBON-α3 and UpWiNs neurons in a standard fly brain Credit: Aso et al.

The new research provides insight into how learned positive and negative values are gradually transformed into concrete memory-driven actions. The UpWiNs also send excitatory signals to dopaminergic neurons for higher-order learning, according to the researchers.

These findings help to explain how parallel dopaminergic neurons and memory subsystems interact to guide memory-based actions and learning at the level of individual neural circuits.   

###

Citation:

Yoshinori Aso, Daichi Yamada, Daniel Bushey, Karen L Hibbard, Megan Sammons, Hideo Otsuna, Yichun Shuai, Toshihide Hige. “Neural circuit mechanisms for transforming learned olfactory valences into wind-oriented movement.” eLife. Posted online September 18, 2023. DOI: 10.7554/eLife.85756

Daichi Yamada, Daniel Bushey, Feng Li, Karen L Hibbard, Megan Sammons, Jan Funke, Ashok Litwin-Kumar, Toshihide Hige, Yoshinori Aso. “Hierarchical architecture of dopaminergic circuits enables second-order conditioning in Drosophila.” eLife. Published February 17, 2023. DOI: 10.7554/eLife.79042