Properties of a motor output system involved in the optomotor response in flies

摘要

1.The optomotor response of tethered flying houseflies (Musca domestica) has been studied at the level of the neural output which controls the activities of some non-fibrillar flight muscles (N-muscles).-a) During visually induced turning responses in a given direction some N-muscles on the right side of the thorax are synergistically active together with other N-muscles on the left side of the thorax. The same muscles are inactive during turning reactions in the opposite direction while the corresponding antagonists are now active (synopsis in Table 1).-b) The response activities of the N-mussles show a considerable variation during the course of time in spite of constant visual input.-c) There is a strong tendency for N-muscle spikes to be phase-locked with respect to the wingbeat period.-d) The findings obtained fromMuscaare in accordance with the corresponding results obtained fromCalliphora(Heide, 1971b).2.TheN-muscle activities have also been investigated in tethered flying blowflies (Calliphora erythrocephala) which tried to yaw spontaneously with both wings beating. In spontaneous left (right) turn reactions the features of the observed neural output are nearly identical with the features of the motor output showing up during visually induced left (right) turn reactions.-A different motor output pattern has been found in flies with only one wing beating.3.The wingbeat synchronous rhythm observed in spike trains from activeN-muscles is produced in the thorax without the participation of higher stages of the fly's CNS. On the other hand no distinct rhythms can be found in spike trains fromN-muscles of non-flying flies when their motoneurons are artificially activated by non-rhythmic stimuli. Afferent information from thoracic sense organs seems to be essential for the production of the rhythm observed during flight.4.The results about the production of the wingbeat synchronous rhythm in spike trains fromN-muscles suggest that the information derived from the motion detectors only acts to gate the output needed to achieve yaw-turn reactions. The strength of the influence of signals from the motion detectors on the output producing system can be modified by the animals “state of excitement”.5.A model is presented which summarizes some features of information processing in the output systems supplying theN-muscles of flies. Available physiological data are discussed in relation to the mo