Control of Optomotor Responses by Descending Deviation Detector Neurones in Intact Flying Locusts

Neural control of optomotor responses in Locusta migratoria was studied using a newly developed preparation of intact, tethered, flying locusts. The preparation could perform normal flight behaviour and head movements while neurones in the neck connectives were recorded and stimulated intracellularly. Course deviations simulated by an artificial horizon caused optomotor reactions, e.g. steering by the wings (monitored as steering reactions in M97 and M127, first basalar muscles of foreand hindwings, respectively) and compensatory head movements. Intracellular recordings were made from two identified descending deviation detector neurones, PI(2)5 and DNC. Both neurones coded direction specifically for course deviations. Electrical activation of either neurone in tethered flight at frequencies of up to 230 Hz elicited steering in M97 and M127 and head rolling with latencies of less than 20 ms. These reactions were of the same quality and strength as compensatory head rolling and steering in M97 and M127 following horizon rolling of about 40°. This demonstrates directly a role of PI(2)5 and DNC in course control.