Researchers detailed a split attractor design for rapidly writing navigational goals in fruit flies. By combining two-photon calcium imaging, hemibrain connectomic data, and wind-controlled behavioral arenas, the study maps how neural circuitry encodes and persists travel directions after odour cues.
Female flies were raised on standard cornmeal-agar medium at 25 °C on a 12-hour light cycle. For optogenetics experiments, researchers supplemented the food with 50 µl of 35 mM all-trans retinal dissolved in ethanol, mixing it with roughly one teaspoon of hydrated potato flakes. Calcium imaging utilized procedures where flies were anaesthetized over ice and a chilled aluminium sarcophagus, then glued onto custom 3D-printed holders.
Wind Control and Odour Patterns in Closed-Loop Behavioral Arenas
Wind direction was managed by a rotary union controlled by a stepper motor and microcontroller, operating in a closed loop based on the flies’ heading measured by ball movement. The starting wind direction was chosen randomly from 0°, 45°, −45°, 135°, or −135°. Wind stayed on from 5–60 seconds during each 65-second trial. Odour signals alternated across five randomized patterns on interleaved trials: an odour step lasting 15 seconds, or odour pulses of 1, 4, 7, or 10 pulses delivered at 1 Hz with a 0.5-second pulse width. When the odour turned off, a compensatory air valve opened to keep total air speed constant.
Connectomic Analysis and Neural Persistence of Walking Direction
Data from the hemibrain connectome were obtained from the neuprint explorer and analyzed using custom Python code. To calculate the persistence of walking direction, researchers defined a goal direction as the mean heading direction adopted in the first second after odour offset or after trial start. They then identified the exact time when flies stopped walking—defined as forward velocity dropping under 0.5 mm per second for at least 1.5 seconds—or when flies deviated from the goal direction by at least 45°.
To calculate the persistence of walking direction, we first defined a goal direction as the mean heading direction adopted in the first second after odour offset (post odour) or after trial start (baseline control), and then identified the time when flies stopped walking (forward velocity under 0.5 mm s−1 for at least 1.5 s) or deviated from the goal direction by at least 45°.
Nature, A split attractor design for rapidly writing a navigational goal
This measurement allowed the researchers to determine how long the flies maintained their intended course before the onset of a stop or a significant change in their heading direction.
