spatial positions, and meaning. Instead, while your unconscious mind is working
feverishly to do all those things, you can relax in bed, recognizing, seemingly without
eort, the lighting xture on the ceiling—or the words in this book. Our visual system is
not only one of the most important systems within our brain, it is also among the most
studied areas in neuroscience. Understanding its workings can shed a lot of light on the
way the two tiers of the human mind function together—and apart.
One of the most fascinating of the studies that neuroscientists have done on the visual
system involved a fty-two-year-old African man referred to in the literature as TN. A tall,