Meeting Abstract
73.6 Monday, Jan. 6 09:30 Sensory and motor determinants of tracking performance in free flight and low light SPONBERG, S*; HALL, RW; DANIEL, TL; Univ. of Washington; Univ. of Washington; Univ. of Washington bergs@uw.edu
In sensory deprived environments such as the low luminance conditions of dusk and night, visual processing limitations can be the primary constraints on performance. Yet the mechanics of how the body responds to neuromuscular commands could still express considerable influence on locomotor performance. We explored these two determinants of performance flight at very low light levels where the hawkmoth, Manduca sexta, visually tracks and forages from flowers subject to continuous perturbations in unsteady air currents. Vertical and horizontal motion detection circuits are separate, but have comparable processing properties. In looming, tracking performance may be poorer due to limitations of detecting visual expansion. If sensing limits performance, then tracking should equivalent in vertical and horizontal directions, while reduced in looming. To test these predictions, we allowed naïve, freely flying moths to feed from a robotically actuated flower, which we oscillated with multiple sinusoids from 0.2 to 20 Hz in any of the three directions. After converting moth and flower movement to the frequency domain, we calculated the ratio of their motion amplitudes (the gain), their relative timing (phase) and extracted a combined tracking error metric. Vertical tracking varied more in gain and showed worse performance at low frequencies. However it did not fall off in phase as quickly as horizontal tracking and performance only degraded above 2 Hz compared to 1 Hz for horizontal. Surprisingly, looming performance was significantly better at low frequencies than either of the other modes due to a more favorable combination of gains and phase lags. We reject the sensory limitation hypothesis. The dynamics of movement are critical determinants of tracking performance even when sensory information is highly constrained.
