Summary: Researchers have revealed how the fruit fly brain converts memories of past rewards into actionable behavior and guides the fly to food. A key area of the brain, the mushroom body, integrates olfactory information and assigns values to odors, but the connection to motor actions was not clear.
This study identifies a cluster of neurons, called UpWiNs, that process these signals, leading the fly to move downwind toward the source of attractive odors. These findings offer a deeper understanding of how memories influence behavior through complex neural circuits.
- Fruit flies turn upwind to track scents, guided by memories of past rewards.
- The mushroom body in the fly’s brain processes odors and assigns positive or negative values to them.
- A newly identified cluster of UpWiNs neurons plays a key role in converting these olfactory memories into upwind movements.
New research by Janelia scientists and collaborators at the University of North Carolina at Chapel Hill shows how a cluster of neurons in the brain of a fruit fly transforms memories of past rewards into actions and helps the fly navigate its search for food.
Like other insects, flies turn into or against the wind to find the source of attractive odors. The fly’s olfactory system detects and smells odors carried by the wind and guides the fly to a reward.
In the fly, an area of the brain 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.
New research shows that reward memories formed in different parts of the mushroom’s body trigger different behaviors, with only some driving the fly’s upwind movement. The study identifies a cluster of neurons—Upwind Neurons, or UpWiN—that integrate inhibitory and excitatory inputs from these compartments, causing the fly to turn and move into the wind.
New research provides insight into how learned positive and negative values are gradually transformed into specific memory-driven actions. According to the researchers, UpWiNs also send excitatory signals to dopaminergic neurons for higher-order learning.
These findings help explain how parallel dopaminergic neurons and memory subsystems interact to control memory-based actions and learning at the level of individual neural circuits.
About this news from neuroscience research
Author: Nancy Bompey
Contact: Nanci Bompey – HHMI
Picture: Image is credited to Neuroscience News
Original Research: Open access.
“Neural circuit mechanisms for the transformation of learned olfactory valence values into wind-oriented movementby Yoshinori Aso et al. eLife
Neural circuit mechanisms for the transformation of learned olfactory valence values into wind-oriented movement
How the brain uses memories to guide future actions is poorly understood. In olfactory associative learning in Drosophila, multiple compartments of the mushroom body act in parallel to assign valence to the stimulus.
Here we show that appetitive memories stored in different compartments induce different levels of upwind locomotion.
Using a photoactivation screen of a novel collection of split-GAL4 drivers and EM connectomics, we identified a cluster of neurons postsynaptic to mushroom body output neurons (MBONs) that can elicit robust upwind control.
These UpWind neurons (UpWiN) integrate inhibitory and excitatory synaptic inputs from MBONs of appetitive and aversive memory compartments. After forming an appetitive memory, UpWiNs acquire an increased response to reward-predicting odors because the response of the inhibitory presynaptic MBON is depressed.
Blocking UpWiNs impaired taste memory and reduced upwind movement during retrieval. Photoactivation of UpWiN also increased the chance of returning to the site where activation was terminated, suggesting an additional role in olfactory navigation.
Thus, our results provide insight into how learned abstract valences are gradually transformed into concrete memory-driven actions through divergent and convergent networks, a neuronal architecture commonly found in vertebrate and invertebrate brains.