ABSTRACT
The neuronal control of flight in dragonflies has been investigated by making intracellular recordings from identified motor neurones, singly and in pairs, in tethered flying and non-flying animals.
All the neuronal circuitry necessary to general flight is contained within the thoracic ganglia.
Large rhythmical fluctuations in membrane potential of flight motor neurones occur during flight. They appear to be generated by intemeurones because there is no evidence that they can be produced by individual motor neurones or by direct interactions between motor neurones. Waveforms in motor neurones that innervate the same muscle are often similar but not identical and a motor neurone may spike several times during a wingbeat. Wave frequency and the phase relation of waves in different motor neurones can change with time.
There are several sources of rhythmical input to motor neurones and each motor neurone receives input from a separate set of interneurones. Non-spiking interneurones have been found.
Pathways of delayed excitation are activated by simultaneous spiking in groups of motor neurones, showing that motor neurones have inputs to interneurones.
Rhythms of two frequencies occur in spiracle motor neurones.
Much proprioceptive information from the wing bases reaches thoracic ganglia and affects motor neurone activity.
It is concluded that, as in the locust, populations of interneurones generate the flight rhythm and drive motor neurones. The diversity of motor neurone activity in dragonflies is presumably related to their well-known aerial manoeuvres.
