The Man Who Wasn't There: Investigations into the Strange New Science of the Self (27 page)

Metzinger’s OBEs stopped after six or seven such episodes. But they have informed his thinking about how the brain might be causing them and what it tells us about the self, eventually resulting in his definitive monograph:
Being No One: The Self-Model Theory of Subjectivity
. The work caught the attention of Olaf Blanke, the neurologist whom I met at the Swiss Federal Institute of Technology in Lausanne.

In 2002, Blanke had induced repeated out-of-body experiences in a forty-three-year-old woman. He had been treating her for drug-resistant temporal-lobe epilepsy. Brain scans did not show any lesions, so Blanke resorted to surgery to figure out the focus of her epilepsy. His team inserted electrodes inside the cranium to record electrical activity from the cortical surface directly, rather than from outside the skull as you would if you were using standard EEG. During this procedure, the woman volunteered to have her brain stimulated using the implanted electrodes. This technique allows surgeons to double-check that they’ve really found the cause of the seizure, while also ensuring that they don’t excise some key brain region. And not just that. The procedure, pioneered by Wilder Penfield, is often the best way to find
out the function of different brain regions, and much of what we have learned about the brain has come from courageous patients who have let themselves be stimulated while conscious. It was during such a procedure that Blanke found that there was one electrode, placed on the right angular gyrus, that, when stimulated, caused the woman to report some rather weird sensations.

When the stimulating current was low, she reported “sinking into the bed” or “falling from a height”; when Blanke’s team increased the amperage, she had an out-of-body experience: “I see myself lying in bed, from above,” she said. The angular gyrus lies near the vestibular cortex (which receives inputs from the vestibular system that’s responsible for our posture and sense of balance). Blanke concluded that the electrical stimulation was somehow disrupting the integration of various sensations such as touch with vestibular signals,
leading to the woman’s OBE.

The next step in studying OBEs in a controlled setting was to try to induce full-body versions of the rubber-hand illusion in healthy subjects in a laboratory. In 2005, Metzinger proposed an experiment to do just that. He teamed up with Blanke and Blanke’s then student Bigna Lenggenhager. The setup they used was simple and elegant. A camera filmed a subject from behind, and the images were sent to a 3-D head-mounted display that the subject was wearing. The subject could see only what was being shown in the display, which was the back of his or her own body, seen in 3-D and about seven feet in front (this was analogous to my seeing the rubber hand rather than the real hand). The experimenter would then stroke the person’s back with a stick. The subjects would feel the stroking on their backs, but would also see themselves being stroked in the head-mounted display. The stroking was either synchronous or asynchronous (to make it
asynchronous, the video feed was delayed a smidgen, so the subject felt the touch first but saw the virtual body being stroked an instant later). Again, this is not unlike the rubber-hand illusion experiment—nor were the results dissimilar.
In the synchronous condition, once the illusion set in, some subjects (but not all) reported feeling the touch in the location of the virtual body about seven feet in front of them and that the virtual body felt like their own.

A few years later, Blanke’s team upped the ante. They rigged a setup that allowed them to conduct the same experiment inside a scanner. The subject was lying down, and a robotic arm stroked the subject’s back. Meanwhile, the subject viewed through a head-mounted display a video of a person being stroked on the back. The robotic arm’s stroking was either synchronous or asynchronous with stroking of the virtual person seen on the display. Again, in some subjects, their sense of location and sense of body ownership were shaken up. One of the most striking outcomes was when a subject reported “
looking at my own body from above,” even though the subject was lying prone, face-up, in the scanner.

“That was for us really exciting, because it gets really close to the classical out-of-body experience of looking down at your own body,” said Lenggenhager, who is now working in Peter Brugger’s group at the University Hospital Zurich.

The subjects were scanned during their experiences, and the scans revealed that their sense of being out-of-body was correlated with activity in the temporoparietal junction (TPJ), a site that integrates touch, vision, proprioception, and vestibular signals. Here was some objective evidence that self-location—where you perceive yourself to be—has to do with neural activity in the TPJ.

When I visited Lausanne, Blanke’s student Petr Macku offered to
try the illusion out on me and I gladly accepted, for that was partly why I was visiting. He used the same equipment, except for a scanner—but I must have been too tense (having just arrived from Paris), and possibly expecting too much, because the illusion didn’t work on me. The other likely explanation is that the full-body illusion is a weak effect, and does not work on everyone. I did feel a bit strange, but that was it.

I was subjected to
yet another full-body illusion in Henrik Ehrsson’s lab in Stockholm (where I had successfully experienced the rubber-hand illusion). In this case, I stood facing a life-size mannequin, mirroring its outstretched hands. The mannequin had cameras for eyes and it was gazing down at its abdomen and hands. The camera output was fed into a head-mounted display that I was wearing. So, I was seeing the mannequin’s abdomen and hands. Arvid Guterstam, the expert manipulator of rubber hands, again did the honors: using two big paintbrushes, he stroked my abdomen and hands, while doing the same to the mannequin’s abdomen and hands, synchronously. I was feeling the touch on my body but seeing the mannequin’s body being touched. Nothing much happened when he was stroking the abdomen (so much for my easily fooled brain), but after a couple of minutes, when he would brush my fingers, I would feel as if the mannequin’s fingers were being touched. I was identifying with the mannequin’s fingers as my own, if not its full body.

Henrik Ehrsson’s team carried out a similar experiment inside a scanner, and subjects reported identifying with the mannequin’s body. Many said they felt that the mannequin’s body was their own. The scans showed that activity in the ventral premotor cortex in both hemispheres, along with activity in the left intraparietal cortex and the left putamen, was correlated with feelings of body ownership, with
the
correlation being strongest for the ventral premotor cortex. It’s known from studies of macaque monkeys that neurons in these regions also integrate vision, touch, and the proprioceptive sense.

What’s clear from these studies is that aspects of our sense of self that we take as given and immutable—a sense of body ownership, a sense of where the self is located, and even the perspective from which the self observes—can be disrupted, even in healthy people.

It’s also becoming evident that self-location, self-identification, and first-person perspective are the result of different brain regions integrating the various sensations—touch, vision, proprioception, and vestibular sensations—to construct these aspects of selfhood. For instance, in the Ehrsson lab version of the full-body illusion, they were able to manipulate a sense of body ownership, and identify the correlated brain regions (mainly the ventral premotor cortex). The Blanke lab version of the illusion messed with perspective and self-location, and that potentially explains why they found a different brain region—the TPJ—as the main culprit.

The exact brain regions aside, the strong message here is that these attributes of self-location, self-identification, and first-person perspective are constructed by the brain. The brain creates a body-centered frame of reference, and everything we perceive is then intimated to us in terms of this frame of reference.

So far, we have been talking of the integration of various external sensations with sensations that tell the brain about the orientation of the body and the location of body parts. But there is another important source of sensations—something we are normally unaware of—which are signals from inside the body, especially the viscera (which contain information about the beating heart, blood pressure, and the state of the gut, for example). We saw in an earlier chapter how these internal
sensations are key to emotions and feelings, and that malfunctions in this pathway can lead to depersonalization and feelings of being estranged from oneself. It turns out that in order to anchor the self to the body, the brain has to integrate signals from within the body with external sensations, and with sensations of position and balance. When something goes wrong with brain regions that integrate all these signals, the results are even more dramatic than out-of-body experiences. They lead to the doppelgänger effect, the kind Ashwin experienced sitting in his car and that caused Brugger’s patient to jump out of a fourth-floor window in Zurich.

One of the most striking aspects of the doppelgänger effect is the presence of strong emotions—and what this reveals about the brain mechanisms involved. Of all the accounts that I’ve heard or read about, none had a stronger emotional content than Chris’s experience, in which his double communicated with his brother, who had just died of HIV/AIDS.

Chris grew up in the San Francisco Bay Area. He was seven years older than his brother, David. As children, Chris and David fought all the time, “as brothers often do.” It wasn’t until Chris moved out of their parents’ house that the brothers realized they missed each other. Over the next decade their relationship deepened. They also had a natural comedic chemistry; they were the “Martin and Lewis of the family,” with David being Jerry Lewis to his elder brother Chris’s Dean Martin. The gags were constant. They made outrageous bets with each other. David took on a bet, for instance, that he could eat an entire two-pound block of cheddar cheese all at once—an effort that had the family in stitches around the kitchen table as they watched David
trying to stuff the cheese into his mouth, eventually just laughing hysterically and drooling melted cheese.

They played a relentless game of “gotcha.” Chris recalled one incident where he got David well and good. David at the time was sporting an Afro hairdo and was sitting and watching TV with the family. Chris had been working on the water heater outside the house when he spied a large alligator lizard, a native California species. Chris caught the lizard and put it into a pocket of the overalls he was wearing. He came back into the house and discreetly maneuvered himself behind David and dropped the lizard on his Afro.

David knew Chris was up to something but was blasé about it. “Then the lizard took off. It ran right across the top of his head, down his face, and jumped onto his chest. My brother just screamed, and levitated off of the chair,” Chris told me. “I swear he was two feet off the ground, screaming all the way across the room.” Once David realized he’d been had, he laughed too, and then everyone spent the next forty-five minutes looking for the lizard. They never found it, dead or alive.

When David turned sixteen, he asked if he could come and spend the weekend with Chris. It was uncharacteristic of him to come for a whole weekend, so Chris knew something was up, and even had an inkling of what. Toward the end of the visit, a nervous David said, “Chris, I have to tell you something.” Chris said OK, tell me.

“I’m gay,” said David.

“Tell me something I don’t know,” said Chris.

“What? You know?”

“I’ve known since you were nine. Come on, how could I not know? I’m your brother,” said Chris.

Eventually, David came out to his parents, who were crushed,
especially their mother. Chris got mad at his parents, and confronted them about whether they saw any difference between him (the straight son) and David. “It kind of smacked them a little bit, stung a bit,” Chris told me. But soon enough, the family came together.

A few years later, David told Chris that he had contracted HIV. “He was running around with a wild crowd over in San Francisco,” said Chris. “There was a lot going on of what you might traditionally expect of San Francisco in the late ’70s and early ’80s.” This was the early days of the HIV/AIDS epidemic, and HIV drugs weren’t as effective. David knew he was dying, so he asked Chris to write his eulogy for the impending funeral.