A psychoanatomical investigation of the blanking phenomenon.

One cannot detect a white disk located at least 15 degrees from fixation in an intersection of gray alleys that define a grid of black squares. A psychophysical examination of the anatomical locus of this "blanking phenomenon" is reported here. Stimuli were presented dichoptically; disk threshold was measured with fixed-step staircases. Three dichoptic experiments were developed employing different stimuli. Simple dichoptic presentations implied both pre- and post-fusion contributions. One follow-up experiment verified pre-fusion contributions, while another implicated post-fusion mechanisms. These results indicate that the blanking phenomenon has contributions from multiple sites in the visual system.