Circuits for integrating learned and innate valences in the insect brain

Area of Science:

• Neuroscience
• Animal Behavior
• Connectomics

Background:

• Animal behavior results from innate predispositions and individual learning experiences.
• The neural mechanisms integrating innate and learned cue valences for action selection remain unclear.

Purpose of the Study:

• To comprehensively map neural connections downstream of mushroom body output neurons and their interactions with lateral horn neurons in Drosophila larvae.
• To identify neurons integrating learned (MB) and innate (LH) valences.
• To elucidate the neural basis of behavior modification through integrated sensory information.

Main Methods:

• Utilized electron microscopy for synaptic-resolution connectome mapping in Drosophila larvae.
• Identified and characterized convergence neurons receiving input from both mushroom body (MB) and lateral horn (LH) pathways.
• Confirmed functional connectivity and behavioral relevance of identified neurons through experimental validation.

Main Results:

• Discovered multiple convergence neuron types receiving convergent MB and LH inputs.
• Identified a subset of convergence neurons integrating excitatory positive-valence and inhibitory negative-valence inputs.
• Demonstrated that these neurons encode integrated odor value and bidirectionally control turning behavior.

Conclusions:

• These neurons act as crucial integration points for learned and innate valences.
• Learning may modulate turning behavior by altering the excitation-inhibition balance on these convergence neurons.
• Provides a circuit-level understanding of how experience refines innate behavioral responses.