Extended Data Fig. 2: Electrophysiological and behavioural verification of optogenetic activation of Drosophila ORNs.

a, Extracellular measurements of ab2A firing rates for various odour signals mimicking those we use throughout our study. Stimuli (red shades) are delivered using a Luxeon Rebel 627 nm red LED (Lumileds Holding B.V., Amsterdam, Netherlands) at 10 uW/mm². The frequency and duty cycle for the stimuli in the first plot are 1.5 Hz and 50% respectively, which mimics what a stationary fly in the 5 cm wide, 15 mm s⁻¹ fast moving bars (Fig. 2b) would encounter. Longer stimuli approximate the stimuli experienced in the wide moving bars (Fig. 2e, f). The bottom plot shows the firing rate in response to the stimulus experienced by one representative measured fly navigating 15 mm s⁻¹ moving wide bars. All recordings were taken from 5 ab2a ORNs in 2 different flies. b, Illustrative track of a fly following stationary fictive odour ribbons upwind. Red bars: optogenetic stimulus location – bars are overlaid on the figure, but not actually imaged since the image is IR-pass filtered. c, Fictive odour signal experienced by a fly (red bars) can be quantified simultaneously with fly behaviour (teal) by aligning the camera and projector coordinate systems (Methods). Plotted are the fictive odour signal and behaviour for the track shown in b. d, Verification that flies on both the top and bottom glass surfaces of the assay respond similarly to the fictive odour signals (here, 3 odour ribbons in laminar wind; scale bar: 2 cm; left). Flies were manually annotated as being on the top or bottom surface. In both cases (middle and right; scale bar: 2 cm), flies followed the fictive odour ribbons upwind, similar to behavioural responses with real odours¹⁰.

Source Data