Invited Session I: Focusing on the Human Fovea: Perception in the foveal rod scotoma.

Abstract

Resources for visual processing, such as the density of cone photoreceptors and the number of neurons in visual cortex, prioritize the fovea to maximize contrast sensitivity and visual acuity under photopic conditions at daylight. Consequently, the fovea does not contain any rod photoreceptors, which are saturated under photopic conditions, but allow for vision under scotopic conditions at dim lighting. Perception in this foveal rod scotoma is particularly interesting given the important role of foveal vision under photopic conditions. Our results show that there is perceptual completion of the foveal rod scotoma under scotopic conditions. Interestingly, humans trust that filled-in information more than veridical information from the peripheral visual field in a metacognitive confidence task. When flickering the background, a blurry counter-phase afterimage becomes visible in the fovea. This afterimage is most apparent at a flicker frequency of about 3 Hz and appears considerably larger than the rod-free zone. These results show that perceptual completion can occur even in the fovea and might not be limited to the absolute rod scotoma.