Identifying the brain's own facial recognition system
The ability to recognize faces is so important in humans that the brain appears to have an area solely devoted to the task: the fusiform gyrus.
Brain imaging studies consistently find that this region of the temporal lobe becomes active when people look at faces. Skeptics have countered, however, that these studies show only a correlation, but not proof, that activity in this area is essential for face recognition. Now, thanks to the willingness of an intrepid patient, a new study provides the first cause-and-effect evidence that neurons in this area help humans recognize faces-and only faces, not other body parts or objects.
An unusual collaboration between researchers and an epilepsy patient led to the discovery. Ron Blackwell, an engineer in Santa Clara, California, came to Stanford University in Palo Alto, California, in 2011 seeking better treatment for his epilepsy. He had suffered seizures since he was a teenager, and at age 47, his medication was becoming less effective. Stanford neurologist Josef Parvizi suggested some tests to locate the source of the seizures-and also suggested that it might be possible to eliminate the seizures by surgically destroying a tiny area of brain tissue where they occurred.
Parvizi used electrodes placed on Blackwell's scalp to trace the seizures to the temporal lobe, about an inch above Blackwell's right ear. Then, surgeons placed more electrodes on the surface of Blackwell's brain, near the suspect point of origin in the temporal lobe. Parvizi stimulated each electrode in turn with a mild current, trying to trigger Blackwell's seizure symptoms under safe conditions. "If we get those symptoms, we know that we are tickling the seizure node," he explains.
Certain electrodes, however, produced a dramatically different result from the colors and memories that Blackwell typically experienced. When Parvizi sent a signal through these electrodes on the fusiform gyrus, Blackwell told him, "You just turned into somebody else. Your whole face just sort of metamorphosed." When the stimulation was halted, Blackwell reported that Parvizi's face had "returned" to normal. The same test caused Blackwell to perceive unsettling distortion in the face of Parvizi's assistant.
But the electrode stimulation affected only Blackwell's perception of faces of people he could see in person. Stimulating the two points also produced no change in Parvizi's suit, tie, or skin color, or in other objects around the room.
While the electrodes were in place, Parvizi got Blackwell's permission to turn the clinical probe into a research study, described online tomorrow in The Journal of Neuroscience. Teaming up with Stanford neuroscientist Kalanit Grill-Spector, who studies the brain areas important in facial recognition, he scanned Blackwell's brain using functional magnetic resonance imaging (fMRI) and confirmed that the two electrodes that influenced Blackwell's perception of faces were at points in the fusiform gyrus implicated by Grill-Spector's previous research. The researchers also recorded brain activity using the electrodes they'd placed on Blackwell's brain with a technique called electrocorticography. They found that the activity picked up by the electrodes at the two "hot spots" tracked with peak activity at these sites, as measured by fMRI.
Cognitive neuroscientist Juan R. Vidal of the Lyon Neuroscience Research Center in France applauds the authors' use of multiple methods and says the study is the first to prove that the fusiform gyrus plays a causal role in face perception. Previous studies only showed that the area is involved, Vidal says. "The complementary evidence of electrocorticography, fMRI, and brain stimulation will make it possible to study not only the effects of brain stimulation on the local neural networks that process face information, but also how they broadcast their information towards other regions in the brain."
- - -
This is adapted from ScienceNOW, the online daily news service of the journal Science. http://news.sciencemag.org
- 1 Migrant crisis: Greek soldier saved 20 people singlehandedly off Rhodes beach
- 2 The confessions of men who ordered mail-order brides
- 3 UK weather: Britain braced for snow as arctic air mass moves in
- 5 'Isis' schoolgirls: Missing British teenager tweets picture of her Syrian takeaway
Migrant crisis: Greek soldier saved 20 people singlehandedly off Rhodes beach
Aaron and Melissa Klein: Oregon anti-gay bakers ordered to pay $135,000 after refusing to make cake for same-sex wedding
UK weather: Britain braced for snow as arctic air mass moves in
Power of Nepal earthquake was equivalent to 20 huge atomic bombs
Nepal earthquake video: Terrifying footage shows moment avalanche hit Everest Base Camp
General Election 2015: Chuka Umunna on the benefits of immigration, humility – and his leader Ed Miliband
The sickening truth about food banks that the Tories don't want you to know
Migrant boat disaster: Ukip candidate mocks victims in sickening Twitter post
Nigel Farage wants the BBC to stop making programmes like Doctor Who, Strictly Come Dancing, and Top Gear
Global warming: Scientists say temperatures could rise by 6C by 2100 and call for action ahead of UN meeting in Paris
General Election 2015: Britain would become a 'communist dictatorship' under Ed Miliband and Nicola Sturgeon, claims wife of Michael Gove
£16000 - £25000 per annum: Recruitment Genius: A Photographer/ Floor planner /...
£30000 - £40000 per annum: Ashdown Group: Front-End Developer - Guildford/Craw...
£13500 - £15000 per annum: Recruitment Genius: A Customer Service Assistant is...
£16000 - £35000 per annum: Recruitment Genius: An ambitious and motivated Sale...