Fig. 4. Effects of leg and abdominal movements on interneuron C₁ activity. (A) Body tilting in the contralateral-side-down direction (i) without a leg substratum when the animal was at rest and (ii) with actively moving legs. The animal body was kept tilted during the recording shown in i and ii. In each part, the top trace monitors muscle activity whereas the bottom trace monitors interneuron C₁ activity. (B) An exceptional case in which the interneuron activity was affected by leg movements in the air. The spike activity during maintained tilt of the resting animal (i) was significantly enhanced when the animal actively moved its walking legs (ii). (C) Effects of abdominal posture movements on interneuron activity. Upward and downward arrows indicate the onset time of abdominal extension and flexion movements, respectively. No noticeable change was observed in interneuron activity during these movements.