Color-specific effects of intense laser exposure on visual evoked potentials in rhesus monkeys

Color-specific visual impairments following exposure to intense laser flashes were investigated using visual evoked potentials (VEPs) recorded from four anesthetized rhesus monkeys. Steady-state VEPs were recorded from the primary visual cortex in response to counterphasing high-contrast sine-wave gratings composed of either luminance contrast (red-black, green-black, and blue-black) or chromatic contrast (red-green). The effects of laser flashes in the red (647 nm), green (514 nm), and blue (476 nm) regions of the visible spectrum were assessed. Only slight wavelength-specific effects were demonstrated, primarily for the red-black grating relative to the other two luminance gratings. Recovery functions for VEPs to the red-green chromatic grating were similar to those of the three luminance gratings. The results are discussed in terms of nonopponent (luminance) and opponent (chromatic) processing.