circuits/Looming escape · giant fibre

The canonical escape reflex: two looming-sensitive populations converge on a single descending neuron that fires once and commits the animal to a jump.

**Computes** Time-to-collision from visual expansion, thresholded into a go/no-go escape decision. **Behaviour** Short-latency take-off. The fastest escape the fly has. **Timescale** Reflex **Pathway** LC4 -> LPLC2 -> Giant fibre (DNp01) -> TTMn / PSI

Stages: - LC4 (input, lobula) — Angular size and expansion rate - LPLC2 (input, lobula) — Looming edges expanding outward - Giant fibre (DNp01) (decision, ventrolateral-neuropils) — One descending neuron per side; pools both inputs - TTMn / PSI (output, t3-leg-neuropil) — Tergotrochanteral motor neuron drives leg extension

The pathway is published anatomy and ships here. The connectivity behind it comes from the source dataset: import a brain to extract the actual neurons and weights.

- The convergence of many LC4/LPLC2 cells onto one giant fibre is a pooling motif with a hard threshold. - A slower, non-giant-fibre escape runs in parallel and produces a better-coordinated take-off.

Cite as: von Reyn et al. 2014; Ache et al. 2019; Dombrovski et al. 2023.