The right side of the brain helps people recognize themselves in a picture, say researchers at Beth Israel Deaconess Medical Center in Boston.
The study joins a growing body of evidence that demonstrates the right hemisphere plays an important role in self-awareness, which scientists believe is one aspect of human consciousness. The research is published in the Jan. 18 issue of the weekly journal Nature.
"It's not an all or nothing phenomenon, but recognizing one's own face appears to be a preferential ability of the right hemisphere," says lead author Julian Keenan, Ph.D., a cognitive psychologist who did the work as a postdoctoral fellow at Beth Israel Deaconess. Keenan is now on a leave of absence from Beth Israel Deaconess and Harvard Medical School, where is is an instructor of neurology. He is working as a visiting scientist in another lab.
In the first part of the study, Keenan and his colleagues worked with five patients who were undergoing preoperative testing for brain surgery to treat epilepsy. In the testing, each half of the brain was briefly anesthetized for up to three minutes so that surgeons could evaluate whether the right or left hemisphere was dominant for speech and memory.
Each patient was shown and asked to remember a morphed computer image blending the patient's own face with the face of a famous person. Each man's photograph was morphed with the face of Bill Clinton or Albert Einstein, and each woman's was combined with the face of Marilyn Monroe or Princess Diana. After the anesthesia wore off, patients were asked to choose which face they remembered seeing, their face or the famous face, although they saw only the morphed image when they were under anesthesia.
While the left hemispheres of the five patients were anesthetized, their right brains could apparently recognize themselves in the morphed images, says Keenan. Once the anesthesia wore off, all five patients remembered seeing their own faces. But after numbing of right hemisphere (and after the left hemisphere "saw" the morphed image), four out of five patients only remembered seeing the famous person.
In a follow-up experiment, 10 healthy people who worked in the Beth Israel Deaconess neurology department each viewed a morphed image of his or her face with the face of a famous person and another one morphing a colleague's familiar face with a famous face. Using transcranial magnetic stimulation applied to the motor cortex near the front of each hemisphere, researchers found significantly greater right brain activity when people viewed a self-morph compared to a co-worker-morph. No such difference was seen when testing the left hemisphere, as measured by sensitive detectors on small tell-tale muscles on the back of each hand.
"One of the astonishing findings in psychology is that humans and the apes (including chimpanzees, orangutans, and some gorillas) are the only species that recognize their own faces in a mirror," says Keenan, who began researching self-awareness as a graduate student. "It has been thought that this ability is a hallmark of consciousness. To know that our own face is ours inevitably requires a knowledge of the self. Without self-knowledge, it would be seemingly impossible to recognize who we are."
Scientists believe studies of self-awareness may provide unique insights into consciousness. Doctors hope eventually to use such information to help people with disorders that include a lack of awareness of self and others, such as schizophrenia, autism and depersonalization syndrome.
"What Keenan and his colleagues have managed to do is demonstrate that by anesthetizing one half of the brain or the other you can literally turn self-recognition on or off," says Gordon Gallup, Jr., Ph.D., professor of psychology at State University of New York at Albany. "This most recent study is one of many that implicate the right half of the brain -- in particular, the right frontal cortex -- as an essential to self-awareness and self-recognition." Gallup developed the original mirror tests of primate self-recognition, and he was one of Keenan's advisors in graduate school at SUNY-Albany.
The researchers don't know exactly what engages the right frontal cortex during self-face recognition, nor precisely what the right hemisphere contributes to self-awareness.
"Keenan has shown that the right hemisphere is contributing something critical for recognition of one's own face," says senior author Alvaro Pascual-Leone, M.D., Ph.D., a behavioral neurologist and director of the Laboratory for Magnetic Brain Stimulation at Beth Israel Deaconess. "We can't say, however, that it's only there that self-awareness takes place. Such a complex phenomenon as self-awareness requires the coordinated function of many different brain areas." Pascual-Leone is an associate professor of neurology at Harvard Medical School.
Beth Israel Deaconess Medical Center is a major patient care, research and teaching affiliate of Harvard Medical School and a founding member of CareGroup Healthcare System. BIDMC is the third largest recipient of National Institutes of Health research funding among independent U.S. teaching hospitals.
The above story is based on materials provided by Beth Israel Deaconess Medical Center. Note: Materials may be edited for content and length.
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