SPECTRAL SENSITIVITY OF MACAQUE MONKEYS MEASURED WITH ERG FLICKER PHOTOMETRY

Macaque monkeys are widely used as a model species for investigations of the biology of human vision. Previous measurements suggest that the cone-based spectral sensitivity of these two primates is greatly simi lar, but perhaps not identical. We measured the photopic spectral sens itivity of 42 male macaque monkeys from two species (Macaca mulatta, M . fascicularis) using an objective index, electroretinogram flicker ph otometry. The variations among individuals and between the two species were very small and there was no evidence for any significant cone pi gment polymorphism in this sample. There are small but systematic diff erences in spectral sensitivity between macaque monkeys and equivalent ly tested human subjects-the monkeys were slightly more sensitive to s hort wavelengths (<520 nm) and slightly less sensitive to wavelengths longer than this value. The results obtained from the curve fitting of standard photopigment absorption spectra to the spectral-sensitivity functions suggest that the difference between human and macaque monkey spectral sensitivity principally reflects differences in the relative proportions of the long-and middle-wavelength cones in the retinas of the two species.