Human Cone Transduction

人眼通过位于眼睛后部的一组特殊的感光细胞和称为视网膜的神经细胞来探测光线。光能是用称为量子的单位来描述的；将光能转化为细胞输出的神经信号称为转导。光感受器内的电反应是由已知最快的化学反应引发的。尽管这些反应的速度很快，但这些细胞输出的总反应时间相当慢，只有十分之一秒，因为有一系列生化反应有效地放大了信号能量。两种基本的光感受器，称为视杆和视锥，在视网膜中发起视觉信号，然后由视神经发送到大脑。圆锥体系统通常用于强光照明下的颜色视觉，而杆状系统对弱光非常敏感，但本身不携带颜色信息。该项目研究人眼视锥传导过程的组成机制，利用人的反应获得高度可控的持续时间和强度的刺激光的阈值。将测量锥体系统在暗适应状态下对单次闪光的响应，不同锥体类型在绝对阈值下吸收的量子数，以及暗适应锥体响应中的不同时间分量。这一新的方法将产生关于正常人类视觉的重要的新的基本信息，这些信息将对进一步理解视觉的一般生物化学和生理学产生影响。

The human eye detects light by a sheet of specialized photoreceptor cells and nerve cells called the retina, at the back of the eye. Light energy is described in terms of units called quanta; the conversion of light energy to a neural signal output by the cell is called transduction. The electrical response within the photoreceptors is initiated by the fastest chemical reactions known. Despite the speed of these reactions, the total response time for the output of these cells is rather slow, to as much as a tenth of a second, because there is a cascade of biochemical reactions that effectively act to amplify the signal energy. Two basic kinds of photoreceptors, called rods and cones, initiate visual signals in the retina which then are sent to the brain by the optic nerve. The cone system is usually used for color vision in strong daylight illumination, while the rod system is very sensitive to low light level but does not carry color information by itself. This project examines the component mechanisms of the cone transduction process in the human eye, using human responses to obtain thresholds for seeing stimulus lights of highly controlled duration and intensity. Measurements will be made of responses to single flashes from the cone system when it is in a state of dark adaptation, of the number of quanta absorbed at the absolute threshold for different cone types, and of the different time components in the dark-adapted cone responses. This novel approach will generate important new fundamental information on normal human vision that will have impact on further understanding the biochemistry and physiology of vision in general.