A common directional tuning mechanism of Drosophila motion-sensing neurons in the ON and in the OFF pathway.

Juergen Haag,Abhishek Mishra,Alexander Borst

doi:10.7554/elife.29044

Abstract

In the fruit fly optic lobe, T4 and T5 cells represent the first direction-selective neurons, with T4 cells responding selectively to moving brightness increments (ON) and T5 cells to brightness decrements (OFF). Both T4 and T5 cells comprise four subtypes with directional tuning to one of the four cardinal directions. We had previously found that upward-sensitive T4 cells implement both preferred direction enhancement and null direction suppression (Haag et al., 2016). Here, we asked whether this mechanism generalizes to OFF-selective T5 cells and to all four subtypes of both cell classes. We found that all four subtypes of both T4 and T5 cells implement both mechanisms, that is preferred direction enhancement and null direction inhibition, on opposing sides of their receptive fields. This gives rise to the high degree of direction selectivity observed in both T4 and T5 cells within each subpopulation.

Highlights

The direction of visual motion is crucial for fundamental behaviors such as mate detection, prey capture, predator avoidance and visual navigation
In a first set of experiments, we used the same driver line as in our previous study (Haag et al, 2016) expressing the Calcium indicator GCaMP6m (Chen et al, 2013) in both T4 and T5 cells projecting to layer 3 of the lobula plate and, having upward motion as their preferred direction
For T4 (Figure 3b) and T5 (Figure 3c) cells projecting to all layers, we found both preferred direction and null direction suppression, with a spatial separation that follows the same pattern: on the preferred side of the receptive field, a clear preferred direction enhancement was observed without any null direction suppression (Figure 3b and c, left column)

Summary

Introduction

The direction of visual motion is crucial for fundamental behaviors such as mate detection, prey capture, predator avoidance and visual navigation. In order to extract local, directional information from moving images, mainly two competing algorithmic models of motion detectors have been proposed (Figure 1a,b) Both models implement a delay-and-compare mechanism where two input signals from neighboring image pixels interact in a nonlinear way after one of them has been delayed with respect to the other. This leads to an output that is larger for motion along one, the so-called ‘preferred’ direction than for the opposite, the so-called ‘null’ direction. If this nonlinear response component is positive for sequences along the preferred direction, and zero for

Methods

Results

Conclusion