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NEUROLOGY Right Brain Appears Quicker Than Left at Spotting SelfThe duality between right and left hemispheres has become part of our lore, with frequent references in popular culture to "right-brain thinking" or "left-brain people." The reality is not so simple, but there is a degree of lateralization in many of the brain's functions, and scientists often treat the left hemisphere as the better half, with its superior abilities in language, problem-solving, and logic. The differences in awareness between the two hemispheres have even been compared to those between humans and other species. But research led by Julian Keenan, HMS instructor in neurology, and Alvaro Pascual-Leone, HMS associate professor of neurology, both at Beth Israel Deaconess Medical Center, shows that self-recognition, one of the hallmarks of human consciousness, may be largely a function of the right hemisphere.
Is it me or is it Bill? Julian Keenan, right, is shown morphed with a picture of Bill Clinton. Patients who looked at similar images of themselves morphed with a famous person recognized themselves in the picture when using their right brain; while using their left brain, patients recognized the celebrity. Photo courtesy of Julian Paul Keenan. When subjects watched a movie showing their own faces morphing with that of a celebrity, the right brain could distinguish between self and other more easily than the left. Where Am I?Although many primates can distinguish faces, the ability to recognize our own face in a mirror is one that only higher primates have, suggesting that self-recognition may be linked to a higher order of self-awareness than simple facial recognition. Research has pointed to the involvement of the prefrontal cortex of the right hemisphere in self-recognition; for instance, functional imaging shows increased activity in the right prefrontal cortex when comparing images of self with others or identifying attributes associated with self. But imaging can be notoriously vague. It shows active areas of the brain but cannot prove a causal relationship.The team's current experiment goes a step beyond looking for correlations by actually blocking a portion of the brain to determine if it is needed for a task. The group studied five patients undergoing a preoperative test for surgery to treat epilepsy. During the test, half of the brain was anesthetized, blocking it temporarily. While under anesthesia, the patients were shown and told to remember an image of their own face morphed with that of a famous person. After the anesthesia wore off, the patients were presented with the two pictures that had been morphed together and instructed to choose which image they had seen. Although neither was correct, patients chose the image they thought most closely represented the one they had viewed. All of the patients who had seen the morphed picture with the left half of their brain blocked chose the picture of themselves. Yet four out of five patients who had looked at the morphed picture with the right half of their brain blocked chose the famous person. "In these subjects, how likely they are to recognize themselves in a given equivocal picture is much higher if they can use the right hemisphere than if they can't," said Pascual-Leone. The Self CenterAlthough the study supports the theory that the right brain is involved in self-recognition, how to interpret this association is still unclear. With an organ as complex as the brain, it is dangerous to assume that an area critical to performing a certain task actually contains this ability. "There is something critical in the relationship of the right frontotemporal area to the self and self-awareness," said Pascual-Leone. "But it doesn't mean that that's where self is." One possibility is that the left brain, with its superior access to language, is able to assign a name to the famous person more quickly, whereas the right brain, which is often linked to the emotional response to language, responds to an unconscious emotional reaction to seeing oneself.Alternatively, or perhaps in conjunction with an emotional response, it is possible that a network in the right brain is involved in many different aspects of self-awareness. Studies of patients with lesions on the right prefrontal cortex also provide anecdotal evidence of this relationship. Case studies have documented people with damage to the right prefrontal cortex who experience impaired autobiographical memory, depersonalization, or denial of ownership of the left side of their bodies. "I'm interested in finding out if there is a relationship in all this," said Keenan. Although there may not be anything so simple as a self "center" in the brain, Keenan said, the current study "allows us to add weight to the notion that some specific area or network that includes right frontal areas has something to do specifically with this idea of self." Keenan has devised other ways of testing the brain's lopsided sense of self-image. His team has used trans-cranial magnetic stimulation on normal subjects to show that the right side of the brain is more active when looking at morphs of oneself. He has also used the techniques of morphing faces to create movies that show a gradual transition from one face to another. Subjects were then instructed to press a button when they recognized that the famous face had become either their own face or the face of a coworker. The average stopping point was sooner when subjects were looking at themselves and responding with their left hand, which is controlled by the right hemisphere. "The question is, when something equivocal is in a face, do you recognize it as being yourself or not and how quickly?" asked Pascual-Leone. —Courtney Humphries |
