Title: Spatiotemporal stimulus properties modulate responses to trajectory changes in a locust

17 The lobula giant movement detector (LGMD) and descending contralateral movement detector 18 (DCMD) constitute one motion-sensitive pathway in the locust visual system that is implicated 19 in collision-avoidance behaviours. While this pathway is thought to respond preferentially to 20 objects approaching on a direct collision course, emerging studies suggest the firing rate is able 21 to monitor more complicated movements that would occur under natural conditions. While 22 previous studies have compared the response of the DCMD to objects on collision courses that 23 travel at different speeds, velocity has not been manipulated for other simple or compound 24 trajectories. Here we test the possibility that the LGMD/DCMD pathway is capable of 25 responding uniquely to complex aspects of object motion, including translation and trajectory 26 changes at different velocities. We found that the response of the DCMD to translational motion 27 initiated in the caudal visual field was a low amplitude peak in firing rate that occurred before 28 the object crossed 90° azimuth that was invariant to different object velocities. Direct looms at 29 different velocities resulted in peak firing rates that occurred later in time and with greater 30 amplitude for higher velocities. In response to transitions from translational motion to a collision 31 course the firing rate change depended on both the location within the visual field and the 32 velocity. These results suggest that this pathway is capable of conveying information about 33 multiple properties of a moving object’s trajectory. 34