Figure 5. Neural output of the optic lobes to moving stimuli precedes behavioral choices.

This figure shows five trials of a single fly in the competing stimuli paradigm. (A) A flying tethered Drosophila has three electrodes inserted into its brain: right (E#1) and left (E#2) optic lobes (OL) and reference (Ref). It flies in a flight simulator seeing identical scenes of black and white stripes on its left and right. (B) When the scenes are still, the fly continues flying strength, and the right and left optic lobes show little activity; only a sporadic spike and the local field potentials (LFPs) are flat (E#2, blue traces; E#1 red traces). (C) When the scenes start to sweep to the opposing directions (ft = 0), it takes about 20 ms (yellow) for the optic lobes to respond to these visual stimuli (first spikes, and dips in LFPs). However, the fly still only makes little adjustments in its flight path, i.e. the yaw torque remains flat. (D) After minimum of 210 ms of stimulation, the fly finally chooses the left stimulus by attempting to turn left (gray area), seen as intensifying yaw torque (downward). The fly's choice of stimulus (left) is taken from the point where a new clear trajectory starts in the torque response, crossing the midline. The time to 1^st-choice varies greatly; thick black traces show trials where the fly took 375 and 700 ms to choose the stimulus. In the presented fast time scale, the changes in the yaw torque show no obvious influence on the neural outputs of the optic lobes. Recordings like this imply that the early neural activity in the optic lobes is predominantly evoked by visual motion. Thus, here it appears neither induced by, nor corresponds to, stimulus artifacts or flight muscle activity. LFPs show means ± SDs.