Sensorimotor Neuroscience: Motor Precision Meets Vision Kit D. Longden, Stephen J. Huston, Michael B. Reiser  Current Biology  Volume 27, Issue 7, Pages R261-R263 (April 2017) DOI: 10.1016/j.cub.2017.02.047 Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 1 Behavioral signals influence the responses of fly visual neurons. (A) A population of visual neurons called HS (single example neuron shown in orange) and VS (green) cells respond to the visual motion that a fly sees when it turns relative to the world. The silhouette of the fly brain is shown in black, with visual neurons projecting from the optic lobe to the central brain. The VS and HS neurons synapse onto motor neurons (not shown) and descending neurons (red) that convey visual information to the thorax where the motor centers for flight and walking reside. This circuit can be modulated at many points, including potentially by octopaminergic neurons (turquoise) and ascending neurons (blue) providing feedback from the thorax. (Example neurons traced from images of stochastically labelled single neurons courtesy of Aljoscha Nern [20]). (B) When a walking fly turns to the left the image of the world moves to the right across its retina. The HS cell on the right side of the brain responds to the resulting visual motion. Fujiwara et al. [6] found that in addition to these cells receiving a visual signal indicating a leftward turn, they also receive a matching non-visual signal during leftward turns (triangles, excitation; circles, inhibition). This novel input ensures that the neuron responds to turns even under conditions where the visual system is unreliable, such as during rapid turns or in the dark. (C) Flying flies perform saccadic banked turns (C1), which contain both roll (C2, rotating about the body’s long axis) and yaw (C3, rotating about the vertical axis) components. When the fly rotates a gaze-stabilizing reflex normally drives the head to follow the direction of the resulting visual motion. HS cells are part of this reflex arc for yaw rotations and VS cells contribute to the same reflex for roll rotations [7,12,13]. During a saccadic turn, the roll component of this gaze stabilization reflex keeps the head level (C2), but the yaw component would interfere by preventing the head aligning with the turning direction (C3). Kim et al. [7] found that the more a neuron is responsive to yaw rotations, the more it is inhibited by an extra-retinal ‘saccade related potential’ (SRP) during a turn. The roll-responsive VS cells are only weakly affected by the SRP during the turn (C2) but the yaw-responsive HS cells are strongly silenced (C3). Kim et al. [7] suggest that this ensures the counterproductive yaw gaze-stabilization reflex is transiently ‘turned-off’ during a turn but the useful roll reflex remains intact. Current Biology 2017 27, R261-R263DOI: (10.1016/j.cub.2017.02.047) Copyright © 2017 Elsevier Ltd Terms and Conditions