Department of Biology, Case Western Reserve University, Cleveland, OH 44106-7080, USA.
Department of Biology, Case Western Reserve University, Cleveland, OH 44106-7080, USA
J Exp Biol. 2018 Oct 15;221(Pt 20):jeb173344. doi: 10.1242/jeb.173344.
The hawkmoth is nocturnally active, beginning its flight activity at sunset, and executing rapid controlled maneuvers to search for food and mates in dim light conditions. The visual system of this moth has been shown to trade off spatial and temporal resolution for increased sensitivity in these conditions. The study presented here uses tethered flying moths to characterize the flight performance envelope of the wide-field-motion-triggered steering response of in low light conditions by measuring attempted turning in response to wide-field visual motion. Moths were challenged with a horizontally oscillating sinusoidal grating at a range of luminance, from daylight to starlight conditions. The impact of luminance on response to a range of temporal frequencies and spatial wavelengths was assessed across a range of pattern contrasts. The optomotor response decreased as a function of decreasing luminance, and the lower limit of the moth's contrast sensitivity was found to be between 1 and 5%. The preferred spatial frequency for increased from 0.06 to 0.3 cycles deg as the luminance decreased, but the preferred temporal frequency remained stable at 4.5 Hz across all conditions. The relationship between the optomotor response time to the temporal frequency of the pattern movement did not vary significantly with luminance levels. Taken together, these results suggest that the behavioral response to wide-field visual input in is adapted to operate during crepuscular to nocturnal luminance levels, and the decreasing light levels experienced during that period changes visual acuity and does not affect their response time significantly.
天蛾在夜间活动，从日落到日落开始飞行活动，并在暗光条件下执行快速控制的机动动作，以寻找食物和配偶。已经表明，这种飞蛾的视觉系统在这些条件下牺牲了空间和时间分辨率，以提高灵敏度。本研究使用系留飞行的飞蛾，通过测量对大视野视觉运动的尝试转向，来表征 在低光条件下大视野运动触发转向反应的飞行性能范围。飞蛾在一系列亮度下接受水平摆动的正弦光栅的挑战，从日光到星光条件。评估了在一系列图案对比度下，亮度对响应一系列时间频率和空间波长的影响。随着亮度的降低，光流反应呈下降趋势，而飞蛾的对比敏感度下限被发现介于 1%至 5%之间。 的最佳空间频率随着亮度的降低而从 0.06 增加到 0.3 周期度，但在所有条件下，最佳时间频率保持在 4.5 Hz 不变。光流反应时间与图案运动的时间频率之间的关系随亮度水平没有明显变化。总之，这些结果表明， 对大视野视觉输入的行为反应适应黄昏到夜间的亮度水平，而在这段时间内光强度降低会改变视力，但对其反应时间没有显著影响。
