Friday, October 26, 2012

Fusiform Stimulation a Turn-Off for Facial Recognition

 Familiar but unrecognizable: Hillary
Clinton and Barack Obama
morphed into one
Epilepsy patients and their doctors have made huge contributions to basic brain science for thousands of years. Hippocrates' seizing patients inspired him to write the first book on neurology, and arguably the first real medical text, in which he insisted that seizures were caused not by spirits, curses, or gods, but by brain dysfunction. Drop the superstition and stick to the facts: that was a radical postion 2400 years ago.

Since then, major studies mapping the functional geography of the human brain, illuminating the mechanisms of memory, exploring the different roles of the right and left hemispheres, and investigating the neuronal mechanisms underlying language were all made possible by epilepsy patients.

With the growing reliance on intracranial studies for screening epilepsy surgery candidates, those contributions are mounting faster than ever. While patients are wired with electrodes--implanted under their skulls so they can read clearly from, and send signals directly to, the brain--for a week or so, so that their doctors can pinpoint the origin of their seizures, there is a lot of basic science that can go on in their heads. If, that is, the patients grant permission and cooperation. Which they often do. With gusto.

A few months ago I wrote about Edward Chang's amazing language experiments at UCSF. Another great example, this one focusing on brain areas devoted to facial recognition, was published in the journal Neuroscience on October 24. (The story was also covered in a good piece by the San Francisco Chronicle's Erin Allday on October 23.)

The study was authored by the brilliant Stanford neurologist and neuroscientist Josef Parvizi, whom I've also written about before. It was serendipitous that the electrodes implanted into his patient's brain were very close to a deeply-buried structure called the fusiform gyrus, long known to play a key role in human facial recognition. When Parvizi administered a brief electrical current to those electrodes, the patient, Ron Blackwell, saw Parvizi's face metamorphose, as if on a bad acid trip. Blackwell's consciousness was not disturbed in any other way, but Parvizi became completely unrecognizable. When Parvizi turned the current off, Blackwell saw his doctor's face return to normal.

It was a temporarily induced case of prosopagnosia, or face blindness, a rare disorder shared by the painter Chuck Close, the primatologist Jane Goodall, and neuroscientist Oliver Sacks. Prosopagnosics often cannot recognize close friends and are sometimes even unable to identify their own faces in the mirror.

Certain kinds of seizures can cause similar facial dysmorphia, possibly by stimulating the fusiform gyrus in the same way that Parvizi's electrical stimulation did.  Australian researcher Jim Chambliss has studied thousands of paintings by epilepsy patients and has found that morphing faces are a very common theme. Perceived facial morphing during seizures may be a more frequent symptom than is generally recognized, says Chambliss.  Some epilepsy patients may be reluctant to report the symptom to their doctors because they may fear the stigma of psychosis.

Parvizi's new research suggests no treatment for prosopagnosia, but it does suggest new avenues of research, he says. As for his patient and collaborator, Ron Blackwell: he never got his surgery. It turned out that his seizures were originating from a point in his brain adjacent to the key area responsible for peripheral vision. Removing the epileptogenic tissue might have damaged Blackwell's vision, Parvizi concluded, and that was an unacceptable risk. Strangely, and wonderfully, though, in the year since Parvizi zapped his fusiform gyrus, Blackwell's seizures seem to be much better controlled by his medication alone. There's no reason to think there's a causal connection, but Blackwell is appreciative to have participated in the study anyway. "I wouldn't take back the experience for anything," he told Allday.

That's typical of epilepsy patients who've donated their brain-time to science. So much of what we know about brains, we owe to their curiosity and generous contributions.




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