"That's funny," I said, "I always thought you were a moron. Guess that just proves you can't tell by looking."
"No, really!" persued New Guy. "That lady in seven? She's got name blindness. Name blindness!"
"And she's cortically blind!"
"And you knew all this before I came in here, didn't you?"
At this point, I felt some pity for The New Guy, even though he consistently addresses himself to my left breast. He's weird; he's not creepy. "Yeah, I kind of figured that out," I said, "but I didn't know the exact names for the problems."
Cortical blindness is an interesting critter. If you have a stroke in your occipital lobe--poor you--there's a chance you might end up cortically blind. If you have that condition, you can't see, but you don't *know* that you can't see. You "confabulate"--that is, you make up stories--in order to fill in the gaps that your now-not-working brain leaves in your visual field.
Strangely enough, cortical blindness can be accompanied by a couple of totally different conditions: blindsight (the ability of a "blind" person to follow movement or recognize facial expressions or avoid objects) or flashes of sight, in which the cortical blindness lifts for a moment or two in particular areas of the field of vision, allowing the person to recognize objects.
This person had all three, along with something called agnosia, or the inability to recognise objects or people. She could tell you what each thing did--for instance, if you put a pen in her hand, she'd hold it and say, "This is something that you use to write with", but "pen" was no longer in her brain.
Blindsight is comparatively easy to explain. Humans have more than one path for vision. If you see, for instance, a threatening face, it's processed through a part of your brain that has to do more with emotion than sight. Likewise, if you are cortically blind and told to run an obstacle course, the signals from your optic nerve--as weird as this sounds--are interpreted by parts of your brain after small, discrete areas of your brain that are dedicated to sensing edges and objects fire off.
Which explains why my sweet patient could follow a fork holding her breakfast eggs (yes, I'm sadistic) while still maintaining that she could see nothing. And why she could avoid the wall and manage to hit the door to the bathroom bang-on, every time.
Name-blindness is another part of the brain, and it's something I still don't fully understand. Interestingly, in this patient's case, it went along with face-blindness. She couldn't recognize her daughter and son-in-law until they spoke, and she couldn't recognize me unless she saw the stickers on my name badge.
That makes me wonder about New Guy. Maybe he's face-blind and can only recognize me by my nametag, which generally rests on my left breast. Maybe if I punched him really hard in the face it would rewire his occipital lobe. You know, a kind of therapeutic coup-contracoup injury.
Thank you, Oliver Sacks. Had I not started reading your work fifteen years ago, I would never have known how to test for agnosia, cortical blindness, or blindsight.