Figure 6.

Mapping behavioral circuits using Split Gal4. (A) Backwards walking (“moonwalking”) in adult Drosophila can be evoked by both mechanosensory and visual stimuli. (B) Two distinct neurons identified by Split Gal4 methods mediate reversal of walking direction: “Moonwalker Descending Neurons” (MDN, magenta) and “Two Lumps Walking Ascending Neurons (TLA, green). (C) Schematic showing the circuitry governing backward walking deduced from several Split Gal4 studies. In addition to the MDN and TLA, essential neurons in the circuit include lobula columnar (LC16) and mechanosensory neurons (TLA), which are sensitive to looming stimuli and touch, respectively, and the “Moonwalker Ascending Neurons” (MAN), which suppress forward walking. (D) Split Gal4 screening to find neurons involved in backward crawling also identified the MDNs (black). Connectomics analysis revealed that a major target of the larval MDNs is a pair of GABAergic neurons in the SEZ, “Pair1” (magenta), which inhibit posterior A27 h premotor neurons (green) required for forward crawling. (E) Schematic showing the larval circuitry responsible for backward crawling (i.e., “mooncrawling”). Panels (A–C) adapted from Sen et al. (2019); panels (D,E) from Carreira-Rosario et al. (2018).