Vitamin A is to create visual cells in order to feel weak light of the composition of rhodopsin, rhodopsin from opsin and 11 - cis - retinal composition, with the dark vision related.

As the monkey looked at the face, blood vessels supplying nerve cells in the visual part of the monkey's brain transiently swelled in exactly the same pattern.

In the visual cortex, where images are processed, cells are grouped by which part of the visual scene they analyze.