Meeting Abstract
The hawkmoth, Manduca sexta is nocturnal and executes rapid controlled maneuvers in dim light conditions. It is known that moth’s compound eyes improve the gain by integrating light spatio-temporally. Though this adaptation improves the brightness of the visual scene it is likely to impose a limit on detectable spatial and temporal frequencies. Despite these limitations M. sexta is known for its flight maneuverability, including hovering, which relies on visual input for control. Our study is aimed at characterizing the flight performance envelope of M. sexta in low light conditions. The experimental design utilizes wide-field motion induced optomotor response as a read out of moth’s ability to perceive visual cues at low light levels. Tethered moths were tested with a horizontally oscillating sinusoidal grating at the following luminance (cd/m2) levels: 70, 10, 1, 0.1, 0.01, 0.001 & 0.0001. We used a range of spatial, temporal and contrast values for the gratings. The optomotor response (i.e., head turning, wing stroke asymmetries, etc.) was recorded using an overhead camera for offline analysis. The contrast sensitivity and visual acuity decreased as a function of decreasing luminance levels. M. sexta responded to spatial frequencies between 0.08 to 0.3 cycles/degree and temporal frequencies between 3 to 5 Hz. Our results are in agreement with previous study on wide-field motion tuning of lobula neurons. These experiments, KP, and MAW were supported by AFOSR grant FA9550-12-0237.
