Fig. 1. FC2 neurons express a stable activity bump in the fan-shaped body during virtual rotations of the fly.
a, Comparing heading angle (grey) and goal angle (purple) to drive turning. b, Schematic of three central-complex structures and the LALs of the fly brain. c,d, Schematics of EPG neurons (c) and FC2 neurons (d). e, Virtual reality setup for recording neural activity in a walking fly. f, Virtual 2D trajectory from a single fly performing menotaxis from which we simultaneously recorded GCaMP activity (26-min recording). An algorithmically detected menotaxis bout is highlighted in black (Methods). Red dot marks the start of the trajectory. g, Trajectories of all menotaxis bouts from the EPG and FC2 imaging datasets. Trajectories were aligned to begin at the same location (red dot). h, Example trace of jGCaMP7f activity of EPG neurons in the protocerebral bridge (PB). Left, EPG ΔF/F0 over time. Middle, bar position (that is, the inverse of the fly’s heading angle) (black) and the EPG phase estimate (grey). Shaded area represents the 90° gap where the bar is not visible. Right, forward walking velocity. The top trace shows a time period during which the fly meandered rather than performing menotaxis. The bottom trace shows a later moment, when the same fly maintained a relatively consistent heading angle. i, Example trace of jGCaMP7f activity of FC2 neurons in the fan-shaped body (FB) (viewed dorsally). j, Experimental paradigm for dissociating heading and goal signals. k,l, Example EPG (k) and FC2 (l) traces during +90° virtual rotations (red arrow). m, Individual ±90° rotation trials (downward red arrows indicate 90° rotation). Top, bar position zeroed at onset of rotation. Bottom, EPG phase zeroed at onset of rotation; thick lines show the mean across flies. Fourteen ±90° trials from 5 flies are shown. See Methods for trial selection criteria. Shaded area marks the 2 s period when the bar was kept stable, at a ± 90° offset, before giving the fly closed-loop control. n, Same as m but for seventeen ±90° rotation trials from 7 FC2 flies. o, Mean phase value during the final 1 s of the open-loop period in m,n. Each dot is the mean for one fly. Horizontal lines depict mean ± s.e.m. across flies. Dashed line shows the expected phase position if the position in the brain of a bump were to track the bar angle. V-test for EPG flies: μ = 90°, P = 7.99 × 10−3. V-test for FC2 flies: μ = 0°, P = 6.65 × 10−4.