Figure 12. LC16 and LC6, but not LC11, respond to visual looming stimuli with robust calcium increases.
(A) Visual stimuli evoked calcium responses of LC neurons were imaged in head-fixed flies. (B) The axon terminals of LC cells bundle to form cell-type specific glomeruli (subset shown in C). We imaged from a single glomerulus by using spilt-GAL4 lines labeling individual cell-types (LC16, LC6 or LC11). Representative regions for calcium imaging experiments are marked with the yellow dashed rectangles. Exemplary responses of LC16, LC6 and LC11 to a slow dark looming disk are shown (C; each single frame taken from the peak response of an individual fly, distinct genotypes were used to image from each glomerulus). (D) LC16, LC6 and LC11 responses to looming visual stimuli are shown for three variants of the stimulus (from top to bottom: dark looming disk, bright looming disk, luminance-matched) expanding at r/v = 550 ms (n = 5 per genotype). Error bars indicate mean ± SEM. Statistics were performed on mean ∆F/F during a time window in which the response peaks (2 s before and after the looming stimulus stops expanding). (E) As a comparison to looming stimuli, we also presented moving object stimuli that contain local motion that is distinct from looming. LC11 responds strongly to the motion of the small (9°x9°) spot, but not the long bar (9°x72°) moving object. The objects moved at 22.5°/s, starting 18° left of the visual midline and stopping 108° to the right of the midline. Statistics were performed on mean ∆F/F during the whole stimulus epoch.
Figure 12—figure supplement 1. LC16 and LC6 are tuned to slower looming speeds.
