Motor Neurone Coupling in Locust Flight
1. Techniques are described for recording in locust thoracic ganglia from single units identifiable as the motor neurones of specific flight muscles. 2. There are at least two kinds of excitatory interactions among flight-muscle motor neurones. A spike in one motor neurone may be electrically transmitted to another with little delay but much attenuation. Stimulation of a group of motor neurones produces a second, probably chemically transmitted, potential with a latency of 5-6 msec. 3. No short-term inhibitory interactions between motor neurones were observed. 4. Activity in one motor unit of the flight system has long-term effects on the motor neurones of other units, excitatory in some cases and inhibitory in others. 5. Single impulses in sensory neurones have little effect on motor neurones; sustained sensory input to a motor neurone produces a slow depolarization and increase in impulse frequency. 6. Antidromic impulses in one group of motor neurones can entrain orthodromic impulses in another motor neurone. 7. These data are discussed with reference to the hypothesis that the pattern of locust flight--rhythmic synchronous bursts of synergist activity, strict alternation between antagonists--can be produced by motor neurone interactions alone.