No binocular rivalry in the LGN of alert macaque monkeys

Orthogonal drifting gratings were presented binocularly to alert macaque monkeys in an attempt to find neural correlates of binocular rivalry. Gratings were centered over lateral geniculate nucleus (LGN) receptive fields and the corresponding points for the opposite eye. The only task of the monkey was to fixate. We found no difference between the responses of LGN neurons under rivalrous and nonrivalrous conditions, as determined by examining the ratios of their respective power spectra. There was, however, a curious "temporal afterimage" effect in which cell responses continued to be modulated at the drift frequency of the grating for several seconds after the grating disappeared.