The (desestimate) providence of prose

During the ultimate period of Dejuni Imaginari, Claridade in 2010, when I decided
spend 40 days with my head in a plaster cast without input images seeing nothing but white, I decided to go through one of most visceral experiencies in my life. My pleasure for reading along with the helplessness of not being able to see to read any of these books pushed me to settle, for one day, injesting only water and pages of a book, chosen for being the most silky-smooth of all them.

While waiting the defecated result for three days, came to my mind how similar and different is the digestive system comparative with visual-cognitive one. While blood absorbs good and necessary nutrients for the body, what in our brain decides which images are good and necessary for us and which not?