?Biological noise? and plasticity of sensorimotor pathways in the locust flight system

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1. Locusts (Locusta migratoria) are flown in a flight simulator in which the relative timing of two flight muscles is used to control the yaw angle. These closed-loop muscles always show a strict correlation to the reference value of the feedback circuit whereas the timing of other muscles (in open-loop) is largely independent of the reference value. 2. The strength of steering reactions in different flight muscles — tested with short imposed yaw stimuli — depends on whether the respective muscles during a particular flight are in closed loop or in open loop within the flight simulator feedback. Closed-loop muscles react stronger to the yaw stimuli than open-loop muscles. 3. Closed-loop and open-loop muscles can be interchanged with one another during a flight. Concurrent changes in yaw sensitivity of the open-loop and closed-loop muscles develop within several minutes of flight. 4. A logical scheme is proposed which explains the specific adjustment of the sensorimotor pathways. It takes into account the spontaneous fluctuations of the motor pattern (‘biological noise’) which serve as ‘ exploratory manoeuvers’ for the muscle specific adjustment of sensorimotor strength.