The physiological basis for contrast opponency in motion computation in Drosophila
Giordano Ramos-Traslosheros1,2, Marion Silies3
1Institute of Developmental Biology and Neurobiology, Johannes-Gutenberg University Mainz, Mainz, Germany.
Nature Communications
|August 18, 2021
Summary
Researchers uncovered how the OFF pathway in Drosophila neurons computes motion. Specific interneurons (Tm2, Tm9, CT1) provide ON stimulus information to T5 neurons, enabling contrast-opponent receptive fields for motion detection.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Insect Vision
Background:
- Direction-selective neurons in Drosophila share computational principles with cortical neurons.
- These neurons utilize contrast-opponent receptive fields with ON and OFF subfields for motion computation.
- The presynaptic circuitry supporting OFF pathway direction-selective neurons remained unclear, especially regarding ON stimulus integration.
Purpose of the Study:
- To elucidate the biological substrate for motion computation within the OFF pathway of Drosophila.
- To identify the specific interneurons responsible for providing ON stimulus information to OFF direction-selective neurons.
- To understand how neuronal circuit elements contribute to contrast-opponent receptive field organization and direction selectivity.
Main Methods:
- Investigated the role of interneurons Tm2, Tm9, and CT1 in the OFF pathway.
- Analyzed the contribution of these interneurons to the receptive field properties of the T5 neuron.
- Examined the persistence of neuronal responses across different behavioral states and the effect of active behavior on spatial tuning.
Main Results:
- Tm2, Tm9, and CT1 interneurons provide essential ON stimulus information to the OFF direction-selective T5 neuron.
- This input supports the development of contrast-opponent receptive fields in T5.
- Variability in Tm9 receptive field properties directly influences T5, and ON stimulus-evoked calcium decrements in Tm9 are state-independent, with spatial tuning sharpened by active behavior.
Conclusions:
- The study reveals how specific interneurons (Tm2, Tm9, CT1) form the biological substrate for motion computation in the OFF pathway.
- The integration of ON stimulus information by OFF neurons is crucial for establishing contrast-opponent receptive fields necessary for direction selectivity.
- Neuronal circuit dynamics, including state-dependent sharpening of spatial tuning, are critical for precise motion detection.
