Parallel pathways convey olfactory information with opposite polarities in Drosophila

Area of Science:

• Neuroscience
• Insect Olfaction
• Behavioral Biology

Background:

• Olfactory information processing in insects involves projection neurons (PNs) transmitting signals from antennal lobes (ALs) to higher brain centers.
• The cooperative function of different PN pathways remains largely uncharacterized, hindering a complete understanding of olfactory information processing.

Purpose of the Study:

• To investigate the role and connectivity of Drosophila GABAergic mediolateral antennocerebral tract PNs (mlPNs) in olfactory processing.
• To compare the function of mlPNs with cholinergic medial tract PNs (mPNs).
• To elucidate how these parallel pathways interact to influence behavior.

Main Methods:

• Examined mlPN connectivity within the ALs, including inputs from olfactory receptor neurons (ORNs) and mPNs, and gap junction interactions.
• Utilized dual-color calcium imaging to simultaneously monitor neural activity in mlPNs and mPNs.
• Investigated the behavioral consequences of altered GABA expression in mlPNs.

Main Results:

• mlPNs receive inputs from ORNs and mPNs, participate in AL network function via gap junctions, and may provide feedforward inhibition to lateral horn (LH) neurons.
• mlPNs show broader odor responses than mPNs, with overlapping but distinct activity patterns.
• Down-regulation of GABA in mlPNs leads to abnormal courtship and aggressive behaviors in male flies.

Conclusions:

• Drosophila utilizes two parallel and interacting olfactory pathways (mlPNs and mPNs) to process olfactory information with opposite polarities coordinately.
• This coordinated processing is essential for the execution of appropriate behavioral responses, such as courtship and aggression.