Meeting Abstract

131.1  Monday, Jan. 7  Background luminance alters tracking performance of freely flying hawkmoths revealing variable delays in optomotor processing SPONBERG, S*; DYHR, JP; HALL, R; SALCEDO, M; DANIEL, TL; Univ. of Washington bergs@uw.edu

Does the context in which sensory signals are acquired and processed alter the performance of motor control tasks? Hawkmoths, Manduca sexta, hover and track moving flowers during natural foraging in variable, low light environments. Neural recordings of motion sensitive optic lobe cells have shown interspecific differences in spatiotemporal tuning properties that correspond to different preferred luminance levels for foraging. These results are consistent with a sensing strategy that integrates visual cues at low light levels. Such a strategy raises the possibility that reducing luminance could increase the time delay for integrating sufficient visual information. Hence performance of motion tracking tasks may vary with the background sensory environment. We tested this hypothesis with freely flying moths feeding from an actuated artificial flower under luminance levels of 0.3 or 300 lux. Flower motion was composed of the superposition of multiple sine waves (0.2-20 Hz), allowing reconstruction of the moth’s frequency response. By calculating the gain, phase delay, and coherence at each frequency, we discovered that moths reliably track at frequencies exceeding 5 Hz. As predicted, we observed significantly lower phase lags between the moth’s response and the flower’s movement under high luminance conditions. This phase difference corresponds to a 16 ms reduction in processing delay at high luminance. At low luminance, moths actually overcorrected, with gains significantly above 1 at peak tracking frequencies (1-2 Hz), possibly due to longer integration delays. The background sensory environment significantly alters the performance of an ecologically-relevant tracking behavior as predicted from sensory neurophysiological mechanisms.