Current injection into interneurones of the terminal ganglion modifies turning behaviour of walking crickets

Abstract

Ascending interneurones of the terminal ganglion of orthopterous insects are known to carry information on wind stimuli perceived by cercal receptors to thoracic and cephalic ganglia. Neurones of these anterior ganglia control evasive walking behaviour. We demonstrate that current injection into individual wind-sensitive local non-spiking interneurones and ascending giant interneurones of the terminal ganglion can influence the orientation behaviour of walking crickets. To induce a change of turning during “wind puff stimulation” by current injection into the lateral giant interneurone, its spike activity has to be modified by at least 100%. In 5 of 12 different types of non-spiking interneurones a moderate shift of the membrane potential results in a change of the mean speed of rotation and/or the frequency of turns. All preparations tested with different amounts of current injection showed a proportional change of turning frequency. Normally, the turning behaviour is evasive with respect to the wind source. During current injection this dependence is preserved, but the general orientation is readjusted. Taking into account known connections between some of these interneurones and ascending neurones the tested wind-sensitive local non-spiking interneurones of the terminal ganglion are likely to impose an offset on the mean direction of orientation controlled by cephalic and thoracic neuronal networks.