Voltage to Calcium Transformation Enhances Direction Selectivity in Drosophila T4 Neurons

Area of Science:

• Neuroscience
• Computational Neuroscience
• Cellular Neuroscience

Background:

• Neural information processing involves converting membrane voltage into calcium signals for transmitter release.
• The impact of this voltage-to-calcium transformation on neural responses to sensory stimuli remains incompletely understood.

Purpose of the Study:

• To investigate the effect of the voltage-to-calcium transformation on neural responses in direction-selective T4 neurons.
• To elucidate how this transformation influences information processing and enhances neural computation.

Main Methods:

• In vivo two-photon imaging in female Drosophila using genetically encoded voltage (ArcLight) and calcium (GCaMP6f) indicators.
• Recording neural responses in T4 neurons to various visual stimuli.
• Developing a computational model to simulate the voltage-to-calcium transformation.

Main Results:

• Calcium signals exhibited significantly higher direction selectivity than voltage signals in T4 neurons.
• A computational model incorporating thresholding, temporal filtering, and a stationary nonlinearity accurately reproduced experimental calcium responses.
• Directional tuning of postsynaptic vertical system (VS)-cells matched the calcium signal in presynaptic T4 cells.

Conclusions:

• The voltage-to-calcium transformation nonlinearly enhances direction selectivity in T4 neurons, contributing to sharpened sensory information processing.
• This cellular processing step, beyond synaptic mechanisms, plays a crucial role in neural computation and information transmission.