Lozada-Perdomo, F. V. | Search bioRxiv

bioRxiv2025

Dual roles of Drosophila reward-encoding dopamine neurons in regulating innate and learned behaviors

Dopaminergic neurons (DANs) play a key role in learning the value of cues that predict reward. The fruit fly Drosophila has provided a powerful model to dissect the mechanisms by which reward-encoding DANs mediate reward learning. However, the role of these DANs in regulating innate behaviors is less clear. Here, we show that activating the entire population of reward-encoding DANs in Drosophila drives innate aversion in multiple behavioral assays, including feeding, locomotion, and spatial preference, even as these neurons confer a positive value onto associated cues to drive future learned attraction. Activating subsets of DANs reveals that the effects on innate and learned behaviors are dissociable. Based on known circuitry, it is likely that innate aversion and learned attraction elicited by DANs arise from distinct effects - direct activation versus synaptic plasticity - on the same target neurons. These results reveal distinct roles for reward-encoding DANs in guiding immediate and future behavior.

neuroscience↗

bioRxiv2023

Overlap and divergence of neural circuits mediating distinct behavioral responses to sugar

A single sensory cue can elicit diverse behavioral responses. For example, the taste of sugar robustly promotes feeding1, 2 but also influences other behaviors, such as altering locomotor patterns to maximize food-finding3, 4 or conferring a rewarding value onto associated contexts or cues.5-7 Here, we investigate how sweet taste elicits multiple appetitive behaviors in Drosophila. Are different sugar-evoked behaviors coordinately regulated? At what point does the sugar circuit diverge into different pathways that drive distinct behaviors? We first established an optogenetic paradigm to study the effects of sugar taste on locomotion, spatial preference, and associative learning. We then tested how different sugar-evoked behaviors were modulated by internal and external factors, including hunger, diet, or the presence of an aversive taste. Different behaviors were generally modulated in similar ways, but we also observed some differences that reveal selective modulation of specific behavioral pathways. Finally, we investigated where the sugar taste circuit diverges into different behavioral pathways. A recent study identified a sensory-motor circuit comprising five layers of neurons that drives the initiation of feeding in response to sugar.8 By individually manipulating each of these neurons, we show that circuits mediating different innate responses to sugar are partially overlapping and begin to diverge at the level of second- and third-order neurons, whereas circuits for innate versus learned behaviors may diverge at the first synapse. Connectomic analyses reveal distinct subcircuits that mediate different behaviors. Together, these studies provide insight into how neural circuits are organized to elicit diverse behavioral responses to a single stimulus.

neuroscience↗