Brains are pretty scary to begin with: they're pinkish gray, they're lumpy, and they blank out at the most inappropriate times. But what would happen if your brain really turned on you?
THAT'S NO FRIEND OF MINE
Do you friends and family feel like strangers? You might be suffering from Capgras' syndrome, a rare condition in which family, close friends, or items of personal significance seem like imposters.
What gives? When you see a familiar face, you don't just recognize the face; you also experience some sort of emotional reaction to it. Capgras' delusion arises when there's a disconnection between these two brain functions. You can identify your father's face and know it's familiar, but since there's damage to the pathway between face recognition and emotional reaction, you experience no jolt of emotion. Since it doesn't feel like your father, the man must be an imposter!
I CAN'T SEE, BUT I CAN SLAM-DUNK
Believe it or not, people with blindsight are blind due to cortical damage, but they can still unconsciously "see" some aspect of their environment.
One famous patient, D.F., couldn't read the big E on the eye chart of identify how many fingers a doctor was holding up right in front of her, but she could put an envelope through a slit in the wall with a high degree of accuracy.
How is that possible? There's more than one way to see. The "what" pathway is responsible for recognizing what an object is - for instance, is it a wolf or a banana? The "where and how" pathway determines where objects are and how to navigate and interact with them. Without visualizing the "what," people with blindsight are still able to figure out the "where."
NOT FOR WEAK STOMACHS
Picture living your life under a strobe light. That's what it feels like to suffer from akinetopsia, or motion blindness. This very rare condition results from selective loss of motion perception because of damage to certain areas of the brain (the temporoparietal cortices). Patients with motion blindness can identify stationary objects and have no problems with other aspects of vision, but moving objects inexplicably seem to appear in one position and then another. For instance, when crossing the street, cars that at first seemed far away could suddenly be very near. And liquid pouring from a pitcher into a cup might look frozen until the cup finally overflowed, allowing the patient to infer that it was full.
BETTER THAN PEYOTE
Can you imagine tasting music or smelling the color red? Most of us can't (or at least don't remember), but those with synesthesia can and do. Just as the word anesthesia means "no sensation," synesthesia means "joined sensation." For some reason, stimulating one sense triggers perception in another sense. For example, a bright light might seem loud, the sound of bagpipe sour, the color after sex a static silver.
No one's sure of the cause, but there are a few hypotheses. Some experts think that crossed wires in the brain cause the problem (the path to the taste buds get hooked up to the sense of hearing path, for example), while others believe that it's a lack of inhibition (the natural pathways that squelch irrelevant sensory input just aren't working properly).
THE MAN WITHOUT A FACE
Prosopagnosics have no trouble recognizing noses, ears, eyes, chins, and so on, but they can't seem to fuse them together into a coherent, whole face. In extreme cases, they can't even recognize their own faces in the mirror. Prosopagnosia results from damage to structures just below the ears, stretching toward the back of the skull (otherwise known as the inferotemporal cortex).
Dr. P., a famous case in the annals of neuropsychology, searched for his hat as he was departing his physician's office only to reach out and grab his wife's head and try to lift it off! Not being able to recognize faces clearly, he apparently mistook his wife's head for a hat.
RENT MEMENTO AND YOU'LL UNDERSTAND
If you haven't seen Memento, check it out. The main character suffers from damage to the hippocampus (one of the memory centers of the brain) and loses the ability to form new long-term memories (his pre-accident memories stay intact, though).
Anterograde amnesiacs live life as though constantly waking from a dream. Leonard, the Memento character, takes to tattooing himself because he can't trust the people around him to tell the truth - even if they did, he'd just forget a few minutes later anyway. Strangely, suffers of this condition can learn new tasks (for example, they improve while taking, say, tennis lessons), but they assume every lesson that it's just beginner's luck.
From mental_floss' book Condensed Knowledge: A deliciously Irreverent Guide to Feeling Smart Again, published in Neatorama with permission. Original article written Shane Pitts and Royce Simpson.
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