McCourt M E, Jacobs G H
Exp Brain Res. 1983;49(3):443-52. doi: 10.1007/BF00238785.
The California ground squirrel (Spermophilus beecheyi) has two classes of cone photopigments (lambda max = 440 and 525 nm). Under photopic conditions about 30% of all optic nerve fibers receives inputs from both cone classes, the remainder are driven solely by the 525 nm cone. Recordings were made from optic nerves in young ground squirrels to trace the development of their spectral responsiveness. Animals were reared from birth in one of three photic environments: white light, darkness, or red light. In the youngest ground squirrels examined (ca. 50 days old) many units receiving inputs from the 525 nm cone were found, but the proportion of units receiving inputs from both cone classes was significantly lower than that of adults. From these initial low levels the proportion of such units increases gradually. Adult proportions were achieved at varying rates which depended on the photic environment in which the animal was reared: animals reared in white light achieved the adult standard earliest, those reared in darkness somewhat later, and the animals reared in red light required much longer to achieve the adult organization. We conclude that: (a) the neural substrates for normal color vision in this species develop to some extent postnatally, and (b) the normal sequence of development can be significantly extended by spectral environments which provide a highly biased stimulation of the two cone mechanisms.
加利福尼亚地松鼠（Spermophilus beecheyi）有两类视锥色素（最大吸收波长分别为440纳米和525纳米）。在明视觉条件下，约30%的视神经纤维接收来自两类视锥细胞的输入，其余纤维仅由525纳米的视锥细胞驱动。对幼年地松鼠的视神经进行记录，以追踪其光谱响应性的发育情况。动物从出生起饲养在三种光照环境之一：白光、黑暗或红光环境中。在检查的最年幼的地松鼠（约50日龄）中，发现许多接收来自525纳米视锥细胞输入的神经元，但接收来自两类视锥细胞输入的神经元比例明显低于成年动物。从这些初始的低水平开始，这类神经元的比例逐渐增加。成年比例以不同的速率实现，这取决于动物饲养的光照环境：饲养在白光下的动物最早达到成年标准，饲养在黑暗中的动物稍晚一些，饲养在红光下的动物需要更长时间才能达到成年结构。我们得出结论：（a）该物种正常色觉的神经基质在出生后有一定程度的发育，（b）发育的正常顺序可被对两种视锥机制提供高度偏向性刺激的光谱环境显著延长。
