Sensory integration in the locust optomotor system-II: Direction selective neurons in the circumoesophageal connectives and the optic lobe

Abstract

Three types of direction selective neurons responding to moving stripes were recorded. Two types, monocular type 1 and 2 neurons in the optic lobe (M1 and M2) and binocular type 1 and 2 neurons in the circumoesophageal connectives, (B1 and B2) are optomotor neurons. The responses of these neurons show the same decrease in magnitude with decrease in the movement amplitude or decrease in the number of stimulated ommatidia as the head movement response. Both type 1 and type 2 neurons show anomalous response to the movements of the single edge which elicits the anomalous optomotor behaviour. The third neuron type, a binocular directional neuron (BD) found only in the optic lobe has no direct relationship with optomotor behaviour. The responses of the optomotor neurons (M1, M2, B1, B2) to movement of a single edge compare well with responses predicted by the behavioural model and confirm the necessity for the new optomotor model in the locust.