Differential Tuning to Visual Motion Allows Robust Encoding of Optic Flow in the Dragonfly.

Area of Science:

• Neuroscience
• Animal Behavior
• Sensory Ecology

Background:

• Wide-field motion-sensitive neurons are crucial for aerial self-motion detection in insects like flies and bees.
• Dragonflies exhibit complex flight behaviors, including hovering and rapid prey pursuit, necessitating broad velocity detection.
• Unlike flies, dragonflies lack halteres, suggesting reliance on visual systems for complex flight control.

Purpose of the Study:

• To investigate motion processing in hawking dragonflies (Hemicordulia spp.) by recording from wide-field motion-sensitive neurons.
• To identify and characterize the properties of these neurons, termed lobula tangential cells (LTCs).
• To understand how LTCs contribute to encoding a broad range of velocities required for diverse dragonfly behaviors.

Main Methods:

• Performed intracellular recordings from hawking emerald dragonflies (Hemicordulia spp.).
• Stimulated neurons with drifting gratings to assess temporal and spatial tuning.
• Analyzed neuronal responses to translated natural scenes to evaluate velocity tuning.

Main Results:

• Identified a diverse group of motion-sensitive neurons named lobula tangential cells (LTCs).
• Observed significant differences in temporal and spatial tuning among LTCs after prolonged visual stimulation.
• Cluster analysis revealed distinct groups of LTCs with varied spatiotemporal tuning, correlating with differences in velocity tuning.

Conclusions:

• Dragonflies encode a broad range of motion velocities through diverse tuning properties of LTCs.
• Variations in LTC velocity tuning ranges and optima are key to encoding different speeds.
• The dynamic tuning of LTCs likely supports the extensive behavioral repertoire of dragonflies, from hovering to high-speed pursuits.