Summary: Researchers revealed how the fruit fly brain transforms memories of past rewards into actionable behaviors that lead the fly to food. A key region of the brain, the mushroom body, integrates olfactory information and assigns values to odors, but the connection to motor actions was unclear.
This study identifies a cluster of neurons, called UpWiNs, that process these signals, causing the fly to move upwind toward the source of attractive odors. These insights provide a deeper understanding of how memories influence behavior through intricate neural circuits.
- Fruit flies face the wind to track odors, guided by memories of past rewards.
- The mushroom body in the fly brain processes odors and assigns them positive or negative values.
- A newly identified cluster of neurons, UpWiNs, plays a central role in converting these odor memories into upwind movements.
New research by Janelia researchers and collaborators at the University of North Carolina at Chapel Hill shows how a cluster of neurons in the fruit fly brain transforms memories of past rewards into actions that help the fly navigate to find food.
Like other insects, flies turn into or against the wind to locate the source of attractive odors. The fly’s olfactory system detects and senses odors carried by the wind and guides the fly to the reward.
In the fly, a brain region called the mushroom body processes and integrates odor information. Several compartments in the mushroom body work 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 that reward memories formed in different compartments of the mushroom’s body trigger 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.
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 explain how parallel dopaminergic neurons and memory subsystems interact to guide memory-based actions and learning at the level of individual neural circuits.
About this neuroscience research news
Author: Nancy Bompey
Contact: Nanci Bompey – HHMI
Image: Image credited to Neuroscience News
Original research: Open access.
“Neural circuit mechanisms for transforming learned olfactory valences into wind-oriented locomotion” by Yoshinori Aso et al. eLife
Neural circuit mechanisms for transforming learned olfactory valences into wind-oriented locomotion
How memories are used by the brain to guide future actions is poorly understood. In olfactory associative learning in Drosophila, multiple compartments in the mushroom body act in parallel to assign a valence to a stimulus.
Here we show that appetitive memories stored in different compartments induce different levels of upwind movement.
Using a photoactivation screen of a novel collection of split-GAL4 drivers and EM connectomics, we identified a cluster of neurons postsynaptic to the mushroom body output neurons (MBONs) that can trigger robust upwind control.
These UpWind Neurons (UpWiNs) integrate inhibitory and excitatory synaptic inputs from MBONs of appetitive and aversive memory compartments, respectively. After appetitive memory formation, UpWiNs acquire enhanced response to reward-predicting odors as the response of the inhibitory presynaptic MBON undergoes depression.
Blockade of UpWiNs impaired appetitive memory and reduced upwind movement during retrieval. Photoactivation of UpWiNs also increased the chance of returning to a location where activation was terminated, suggesting an additional role in olfactory navigation.
Thus, our findings 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.