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Flying locusts respond to changes in wind-velocity or wind-angle with abdomen posturing in the vertical or horizontal plane, respectively. Receptor hairs on the head sense these wind parameters and evoke the responses in specific abdominal muscles. Records were made from individually identifiable motoneurones to these muscles during the performance of wind-evoked behaviour. During flight these motoneurones are excited by the central flight oscillator and show a burst rhythm at flight frequency. Wind stimuli modulate the number of spikes per burst in this rhythm, but do not affect its frequency or phase with respect to the wingbeat. Changes in wind-velocity and wind-angle evoke different relationships of muscle synergy and antagonism, resulting in the two different patterns of behaviour performed by the same group of muscles. During flightless periods the motoneurones show no flight rhythm, but only the much lower frequency ventilatory rhythm. At these times they are unresponsive to wind stimuli.

No machine is capable of reproducing muscle synergy and proprioception. Articulators can be adjusted to the positional records as secured from the patient, but they can only approximate mandibular movements. Many of the errors incorporated in articulators result from the attempts to use one set of guides for all of the selected articulator movements. Insufficient range of adjustment is allowed in these instruments for the duplication of the mandibular movements. Even when sufficient adjustments are included in the articulator, each adjustment cannot be set by direct, independent measurements of the corresponding value in the head. Instead, articulators are set by indirect measurements which often are composite indications of several dimensions. Hence, the significance of the theoretically increased accuracy of the more adjustable instruments is questionable. The optimal number of adjustments which should be incorporated in an articulator has not yet been determined by clinical evaluation.