NEURAL CONTROL OF HINDLEG STEERING IN-FLIGHT IN THE LOCUST

Corrective flight steering with the hindlegs was investigated in intac t tethered flying locusts inside a wind tunnel as well as in animals d issected for intracellular recording and showing fictive flight activi ty. In intact tethered dying animals, activity in the second coral abd uctor muscle (M126) was highly correlated with hindleg steering and wa s coupled to the elevator phase of the flight cycle. Fictive flight an d steering could also be elicited in animals dissected for intracellul ar recording of motoneurones innervating M126. During fictive flight a ctivity, motoneurones 126 were rhythmically excited in the elevator ph ase, presumably from central elements of the neuronal oscillator gener ating the flight motor pattern, as is the case for motoneurones innerv ating wing muscles, During fictive straight flight, this input was sub threshold, and it could be demonstrated that simulated deviation from the flight course resulted in recruitment of motoneurones 126. Statist ical analysis of the latencies of fast muscle spikes in M126 and in on e wing elevator muscle showed that both received common input during f light steering. One source of this common input was identified as the sensory information from the lateral ocelli, which play an important r ole in the detection of course deviation. The experiments demonstrated that processing in the sensory-motor system for hindleg steering is p robably organized in a very similar way to that responsible for steeri ng with the wings.