Central Control of An Insect Sensory Interneurone

Abstract

The T fibre habituates little to a series of sine-wave pulses, and recovery is complete within 10 min. Both response level and rate of habituation are increased when the posterior thoracic ganglia are disconnected from the prothoracic ganglion. This indicates that response level and rate of habituation are maintained at a low level in the intact animal by an inhibitory input or inputs to the prothoracic ganglion, which arise within the pterothorax. These inputs are entirely central in origin, and are independent of extratympanal sensory input. The function of the posterior branch of the T fibre to the posterior thorax may be to initiate a feedback loop which is completed by the input from the posterior thorax. It is suggested that such feedback stabilization of the response level would reduce loss of directional information at high stimulus amplitude, preserve discrimination at high stimulus repetition rates and reduce habituation. The implications of these findings for a warning neurone system are discussed.