Campus & Community

Scientists look people in the ‘I

7 min read

Best place to locate the 'self' is in the brain

Photo of
Alvaro Pasual-Leone uses a magnetic "wand" to briefly disrupt different parts of the brain of a volunteer. Brain scans done during such experiments show that the right side of the brain, behind the forehead and temple, is critical for recognizing one's own face. (Staff photo by Jon Chase)

If you train a monkey to look in a mirror, then put a dab of odorless red dye on its eyebrow, the monkey will try to rub the dye off the mirror. If you do the same with a chimpanzee, this more advanced ape will wipe its own eyebrow.

This simple test is an indicator of self-awareness.

“The chimp is aware of its own mental state; the monkey is not,” says Alvaro Pascual-Leone, associate professor of neurology at the Harvard Medical School. “The ape can access a whole series of individual and social behaviors that lie outside the mental reach of the monkey.”

Psychologist Julian Keenan, Pascual-Leone, and their colleagues have devised experiments to learn how self-awareness arises in humans. They seek a scientific answer to a question posed by 16th century philosopher René Descartes: “What is this ‘I’ that I know?”

Pascual-Leone works with epileptic patients at the Beth Israel Deacones Medical Center, a Harvard teaching hospital in Boston. He carefully scans the brains of these patients to find areas that control memory and language. These places must be avoided during surgery that treats their epilepsy.

Five such patients gave him permission to piggyback a self-awareness test on this preoperative procedure. “In a sense,” he says, “we borrowed their illness. And we are very grateful that they let us use it.”

A human brain consists of two hemispheres connected by thick cables of nerves. The researchers administered an anesthetic first to the front of one hemisphere, then to the front of the other. While one hemisphere slept, the other was shown a composite picture of the brain’s owner morphed with that of a famous person like Marilyn Monroe or Bill Clinton.

When the anesthetic wore off, the experimenters showed the patients’ pictures of themselves and of the famous person, and asked which they saw while one half of their brain slept. They hadn’t, of course, seen either one, but they had to make a choice. (Brain regions drugged by researchers were not near areas where epileptic seizures occurred, so their illness would have nothing to do with the outcome.)

All of those who saw the composite with the right side of their brain awake chose their own picture. Those with the left hemisphere awake overwhelmingly (four out of five) picked the celebrity.

Thus, the right hemisphere, usually considered the emotional side of the brain, must be critical for seeing one’s self in a picture, while the left side, usually thought of as a seat of logic, is not so attuned to the self. (All the subjects were right-handed; things might come out different with lefties.)

Self centers

Does this mean that our self-awareness is centered on the right side of our brains, behind the forehead and temple, at least in most right-handed people? “The frontal part of the right hemisphere is critical for recognizing ourselves,” Pascual-Leone answers. “People with damage to that area have problems remembering things that relate to themselves or with being in touch with their own person. But this doesn’t mean that’s where the self is.”

He and Keenan think that answer is too simple. “I doubt if any one function is centered in a particular part of the brain,” Pascual-Leone says. “We know it’s not true for memory and language. Like those functions, we believe ‘self’ arises from the interaction of different areas in the brain. Although the right frontal area is essential for a healthy ‘self,’ it’s not the whole story.”

One possibility would involve interplay with the limbic system, substructures deep in the center of the brain that govern emotion. There’s a lot of scientific suggestion and some evidence, but no proof, that this emotional part of the brain and the right frontal cortex act together to generate self-consciousness. Descartes might have said, “I feel what I think, therefore I know who I am.”

A striking bit of evidence for a connection between the frontal cortex and emotional behavior comes from the bizarre story of Phineas Gage. In 1848, during construction of a railroad in Vermont, an accident drove a 31/2-foot iron rod into Gage’s face between his jaw and cheek. About an inch in diameter, the rod passed through his face and the front of his brain, exiting through the top of his skull.

Remarkably, Gage survived. He suffered no obvious impairment of sight, movement, speech, learning, memory, or intelligence. But he became a different man. Once responsible, intelligent, well-adjusted, and well-liked, Gage became profane and capricious; he could not be trusted and offended everyone around him. Gage lived another 13 years, wandering about the country and never holding a responsible job.

In the words of his former friends, “Gage was no longer Gage.” He had lost his original sense of self.

Making virtual patients

To probe more deeply into how the self operates, Keenan, Pascual-Leone, and their team briefly disrupted the brains of 10 normal volunteers. They used strong but harmless magnetic fields to induce electrical changes in precise areas of the brain. While the volunteers looked at composite photographs of themselves and famous people, parts of their right or left hemispheres were disorganized with magnetic stimulation for a half-second or less. This setup revealed significantly more activity in the front of the right hemispheres of people when pictures looked more like themselves than when they looked like someone else.

Keenan then created movies showing a gradual transition from a famous or familiar face to a self-face. At the point where a subject recognized his or her own face, he or she pressed a stop button with the left or right hand. To evaluate the result, you must know about a peculiarity of human anatomy, namely that the right side of the brain controls the left hand and vice versa. When the left hand of a right-handed person makes a move, the right side of the brain guides that movement.

This neat little experiment showed that the right hemisphere is faster at recognizing self than the left. It also showed that the left hemisphere more quickly recognizes the self than a celebrity or a familiar friend. In other words, everyone is faster at picking his or her face out of a crowd than any other face.

It’s nice to know how your brain finds yourself, but does it have any practical value?

“Understanding the brain essence of self-awareness helps us come closer to understanding what makes us conscious human beings,” Pascual-Leone answers. “We are able to reflect on ourselves and our actions. We are able to project intentions into the actions of others. Without such knowledge we have an impaired relationship with our social surroundings.”

That happens in some mental illnesses, like autism and schizophrenia. Autistic people, for example, lack an emotional response to self. “Understanding more about what goes on in the brains of such people is a first step to treating their illnesses, in bridging the gap between abnormal and normal,” Pascual-Leone says.

Experiments will continue in an effort to find out how the rest of the brain interacts with the right frontal area to generate self-awareness. Keenan now does this kind of probing at the Mt. Sinai Medical Center in New York City. In Boston, Pascual-Leone continues to search for connections between the thinking and emotional parts of the brain. He believes that “the right frontal cortex provides a window to the emotional or limbic area deep in the center of the brain. I see a bridge between these two regions, between the cognitive and the emotional. I think it is necessary to cross that bridge to gain a sense of self, to find the ‘I’ that we know.”