SPRAYBERRY, Jordanna D. H.; University of Washington: Response of descending visual interneurons in the hawkmoth Manduca sexta to flower-like stimuli

Vision is a vital sensory system in the control of animal flight. Hawkmoths rely on vision to guide flower tracking, a behavior that compensates for flower motion during feeding bouts. What visual information about a moving flower does the hawkmoth nervous system use to modify motor ouput, thereby tracking the flower? Using single unit recordings, I characterized the response of descending visually sensitive neurons in the cervical connectives of the hawkmoth Manduca sexta to animated flower stimuli. Recordings from sixteen descending object sensitive neurons show they are typically not direction specific. They often have multiple preferred directions on several motion axes (horizontal, vertical, and looming). These descending object sensitive units need to respond to sensory signals in a manner that effectively communicates with and does not disrupt the function of motor centers. From this perspective broad direction sensitivities make sense. A hawkmoth has to move in several motion axes to track a flower moving in one axis. In order to accomplish this descending object sensitive neurons may activate multiple motor steering pathways in response to flower motion. Object sensitive units respond to animated flowers moving at many frequencies, but do not exhibit distinct tuning or preference for a particular frequency of motion. However, descending object sensitive neurons appear to have a monotonically increasing response to increasing amplitudes of animated flower oscillation. These data support a reactionary model of flower tracking, where the visual signal of a moving flower directly turns on a motor pathway to move the moth in the appropriate directions, as opposed to calculating trajectories of flowers and matching a flight path to that trajectory.