Mechanisms for the Production of the Motor Output Pattern in Flying Locusts

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Abstract
1. The normal flight pattern consists of alternating bursts of activity in the elevator and depressor motor neurons. However, when sensory input depresses elevator activity, rhythmic bursts of activity in the depressor motor neurons may continue even after all elevator motor neuron activity has apparently ceased. Thus interactions between the antagonistic motor neurons apparently are not necessary for the production of the rhythmic bursts. The proposed mechanism for producing these rhythmic bursts depends on the excitatory interactions among the synergistic motor neurons. Alternative or supplementary explanations for the data seem to be possible only if interneurons participate in the generation of the flight pattern. 2. During flight initiation, when there is a burst of activity in several depressor motor units simultaneously there usually is a pause in the on-going elevator activity; often the normal flight pattern begins at this time. This reciprocal relationship of activity in the antagonists suggests inhibitory coupling between antagonistic motor neurons or between interneurons which may drive them. This coupling may be responsible for the alternation of the bursts of activity in the antagonists during normal flight. 3. There is no evidence for greater co-ordination within a thoracic ganglion than between ganglia. Some activity in the abdominal C.N.S. is also well co-ordinated with the flight pattern. Thus the anatomical separation into ganglia does not correspond to any interruption of the functional integration of the flight system.