Wednesday, April 20, 2011

Prosopagnosia, the Wired Article

There is a very good article by Joshua Davis in Wired Magazine that reviews what it is like to be "face blind" and the research done by Brad Duchaine to establish modern understanding of the disease:
TO CONDUCT HIS FIRST INTERVIEW with Bill Choisser, Duchaine had to drive his red 1988 Camry 300 miles north to San Francisco. It wasn't easy for him. He'd been playing too much V8, a car combat videogame, and driving on a real freeway now gave him panic attacks. He'd pull over to calm himself down. It took a long time to get there.

When he did arrive, Choisser was clearly uncomfortable. Duchaine asked if everything was OK, and Choisser said he couldn't read Duchaine's expressions. It would help if he had a beard – facial hair made faces easier to comprehend.

So three weeks before each of his next eight road trips to San Francisco, Duchaine stopped shaving. He also cut back on playing V8, decreasing his freeway anxiety. He'd show up at Choisser's door with a scruffy beard and a newfound confidence, ready to run his subject through face-recognition tests, some of which he'd just invented. Once back in Santa Barbara, he would run the tests on dozens of grad students and faculty to generate averages for a representative sample. When the numbers came in, it was clear that Choisser's facial-recognition system was severely impaired.

Next, Duchaine tested Choisser on his ability to recognize small differences between the same type of objects. In one exam, Choisser was asked to memorize the details of a particular house. Duchaine then showed him 150 pictures of other houses and randomly threw in images of the original. Choisser consistently identified it. He did the same in similar tests that used shoes, horses, cars, and natural landscapes. It was strong evidence that the brain's system for processing faces is separate from its system for discerning other objects.

The finding was controversial. "People love to carve up the brain and say, 'There's a hand area, there's a face area, and there's a love area,'" says Michael Tarr, a Brown University vision researcher who is one of the leading proponents of an alternative theory. Tarr believes that the fusiform face area is part of a generalized recognition system that gets switched on when someone develops enough expertise to distinguish between two very similar things.

"The discovery of otherwise healthy people living with prosopagnosia is the most exciting development in the field in a long time," Tarr says. "But we can't rely on neuropsychology to figure out what's going on, because you're just asking people questions. You're not getting in there and finding the damage."

The problem is that scientists aren't able to cut open someone's head, plug in electrodes, and test every neuron in the fusiform face area. But as Duchaine's work progressed, fMRI testing indicated that developmental prosopagnosics – those, like Choisser, who were born with the condition – had a smaller face area than normal. One study found that the neural pathways leading out of the face area might be damaged. But none of the tests explained the structure of the face-processing system itself. The best that could be done was to develop visual tests that narrowed down the nature of the impairment and then try to deduce what was going on inside the brain.

Using Choisser's group, now hosted on Yahoo, as a resource, Duchaine contacted and tested other developmental prosopagnosics and began piling up evidence that, with a bit of practice, they could distinguish between very similar objects. In other words, they could learn how to differentiate objects but not faces. The implication: Facial recognition was a hardwired aptitude that did not depend on learning.
There is much more. Go read the whole article.

You can see Bill Choisser's web-based memoir, Face Blind!, here. And Brad Duchaine's research web site.

The article by Joshua Davis is full of vignettes of this tragic condition with stories like this:
TOM UGLOW, A GRAPHIC DESIGNER in London, didn't have a problem perceiving that it was a girl watching him across the bar. Her blond hair had a nice sheen. She seemed pretty. Uglow ordered another beer, downed it, and walked her way. He was about to introduce himself when she cut him off.

"Hi, Tom," she said, no longer smiling. "Why were you making eyes at me?"

"Damn," he thought. "This isn't going as planned."

Her voice sounded familiar. He searched her face but couldn't place her. This happened more than he liked to admit.

"How've you been?" he asked, casually trying to fish for a clue as to who she was.

"Better now that we're broken up."

Ah! It was his ex-girlfriend. Once he'd had a moment to process her voice, he was able to place her. They had dated for a year. Definitely not a good person to be hitting on. It was a problem: Every time he saw a face, it felt like it was for the first time.
Tom Uglow has a web page with this video of him:

I have more than a passing interesting in face blindness: My mother had a brain tumor and the surgery resulted in a hematoma, that is blood in the brain, and that kills brain cells. As a result she had left neglect and other cognitive deficiencies, among them was an inability to recognize people (including her own children). I never got to explore this and talk to her about it. She died within three weeks of the "life saving" operation at the hands of a surgeon who assured me that this was a simple operation for which he couldn't think of any complications!

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