Scotopic thresholds of rhesus monkeys at different grating densities under normal and low-protein diets

Scotopic thresholds of rhesus monkeys were determined over a range of luminance levels, from 1138 to 17.8 x 10(-9) cd/cm2, and grating densities, from .132 to 1.58 lines per cm. The effects of a low-protein diet on these thresholds were also investigated, and standard stimulus objects within the discrimination learning situation were employed. Obtained thresholds decreased systematically from about 350 to 20 x 10(-9) cd/cm2, and there were no significant differences due to dietary protein level.