Neural Mechanisms Underlying Axial/Appendicular Steering Reactions in Locust Flight

Abstract

SYNOPSIS. Steering during flight in the locust involves complex changes in wingbeat, bending of thorax and head, and ruddering movements of abdomen and hindlegs. Most of these behavioral subcomponents involve coordinated modification of axial and appendicular musculature control. Some of the mechanisms underlying this neural modification have been analysed at the cellular level. During steering via wingbeat, sensory information about course deviations leads to highly coordinated and asymmetric changes in the flight motor's output through the following mechanisms. Identified feature detector neurons in the locust brain integrate sensory information concerning specific types of course deviation. Each of these descending detector neurons makes connections with a population of thoracic interneurons. These thoracic interneurons have two important properties. First, they relay deviation information to flight motoneurons. Second, they are under the gating control of the flight central oscillator. Through this gating control the descending sensory signal is phase-coupled to the flight rhythm and delivered to appropriate flight motoneurons in one and the same step. Although most of the recent cellular studies have been aimed at unraveling the neural basis of wingbeat alterations, similar (but not identical) principles of neural organization seem to be involved in the steering reactions produced by axial motor systems.