蜻蜒运动检测神经元的光谱反应

蜻蜒腹神经束上存在着自运动检测神经元和目标运动检测神经元.我们采用了两种视觉刺激条件来测试自运动检测神经元的光谱反应.当采用控制强度和波长的闪光进行测试时、它们的光谱反应曲线与绿色光感受器的光谱灵敏度曲线极其相似,峰值位于500nm处.然而采用运动的条纹进行测试时,它们的峰值却位于560nm处.当用一种颜色的运动图案作为目标放置在另一种颜色背景的前方测试时,发现存在某个目标的照明强度值能使反应下降到自发放电的水平,这表明自运动检测器无法检测这二种颜色的差别,即它们是色盲的、它主要接受来自绿色光感受器的信号.目标运动检测神经元的光谱反应特性与自运动检测神经元的不同,目标运动检测神经元在以380nm至580nm的范围中有着平坦的光谱反应曲线,有时在紫外频段出现峰有(?)前景与背景颜色不同且固定背景光的颜色与强度而改变前景的光强时,神经元的反应不会下降到自发放电水平,当背景为绿色而目标为另一个颜色.特别是兰色时,神经元反应强烈,但当背景为兰色而目标为绿色时,它们的反应相对较弱.这些结果表明目标运动检测神经元是对颜色敏感的.

THE SPECTRAL RESPONSES OF MOTION SENSITIVE NEURONS OF DRAGONFLY

Self-motion detectors of the draonfly ventral cord have large fields that are sensitive to whole-field one way motion with little habituation to the motion. When testing with a flash of controlled intensity and wavelength, the self-motion neurons have a spectral sensitivity similar to that of photoreceptors with a peak in the green near 500nm, but when tested with a moving edge, they have a single peak near 560nm. When tested with a moving pattern on a background with self-motion neurons there is a value of brightness of the foreground so that it cannot be detected against background even for two difierent colours. They behave towards a pattern of two colours as if they are monochromatic, as know for motion perception measured behaviourally or from single neurons in other insects with colour vision.The object - motion neurons have an average spectral sensitivity curve which is rather flat from 380nm to 560nm For object- motion neurons the situation is quite different When the foreground and the background have different colours, there is no valve of the foreground brightness which gives a null response, however the value of the foreground brightness is adjusted But there is a value of the foreground brightness at which the responses of the object-motion neuron reach spontaneous level when the foreground colour and the background colour are the same. The optimum performance for seeing a coloured object appears when the background is green and the object is another colour, discrimination of the object is less effective when the object is green. This result suggests that limit motion detectors are colour coded and the green ones feed into the background system.