Course correction circuitry translates feature detection into behavioural action in locusts

Abstract

Like other flying animals, locusts must maintain course stability despite turbulence and motor errors. Accordingly, they must detect course deviations and then correct them. The compound eyes, the ocelli and the cephalic wind hairs all detect different sensory consequences of flight instability^1–3,and descending interneurones bring this information to the thorax^4–9. One such interneurone of this population (the tritocerebral commissure giant neurone) is known to elicit correctional steering¹⁰.Here we characterize three additional pairs of descending deviation detector neurones and show how their information is translated into altered drive to the flight motoneurones. The central pattern generator for flight^11–13,modulated by proprioceptive feedback¹⁴, gates the signal of the detector neurones in thoracic premotor interneurones⁹,ensuring that the flight motoneurones are affected only during flight. Further, the gating process transforms the phase-independent information of the deviation detectors into a phase-dependent signal modulated at wing-beat frequency, and transfers it to those flight motoneurones active at the time and appropriate to the corrective action required.