SELF REFLECTION: Bodily illusions teach neuroscientists about the sense of self.
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Where are you right now? Maybe you are at home, the office or a coffee shop—but such responses provide only a partial answer to the question at hand. Asked another way, what is the location of your "self" as you read this sentence? Like most people, you probably have a strong sense that your conscious self is housed within your physical body, regardless of your surroundings.
But sometimes this spatial self-location goes awry. During a so-called out-of-body experience, for example, one's self seems to be transported outside the physical body into a surreal perspective—some people even believe they are viewing their bodies from above, as though their true selves were floating. In a related experience, people with a delusion known as somatoparaphrenia disown one of their limbs or confuse another person's limb for their own. Such warped perceptions help researchers understand the neuroscience of selfhood.
A new paper offers examples of rare bodily illusions that are not confined to a single limb, nor are they complete out-of-body experiences—they are somewhere in between. These illusory body perceptions, described in the September issue of Consciousness and Cognition, could offer novel clues about how the brain maintains a link between the physical and conscious selves, or what the researchers call "bodily self-consciousness."
"These reports could be interesting for us to better understand how the brain produces ownership of the entire body—a sense that we have a body in the first place," says Henrik Ehrsson, a neuroscientist at the Karolinska Institute in Sweden who was not involved in the new study.
Lukas Heydrich, a cognitive neuroscientist at the Brain–Mind Institute (B.M.I.) in Lausanne, Switzerland (which is part of the Ecole Polytechnique Fédérale de Lausanne), and his colleagues recruited two epileptic patients from the University Hospital of Geneva. The researchers gave the patients a full diagnostic workup, including neurological and psychiatric examinations, various brain scans using electroencephalography (EEG) and magnetic resonance imaging (MRI), along with structured interviews focusing on aspects of bodily self-consciousness.
Patient 1 was a 55-year-old man who had suffered from epilepsy since he was 14 years old. For nine years the man also endured reoccurring attacks of strange bodily sensations that always followed the same pattern. First, without warning, he would feel an increasing pressure all along his left side, which escalated to the point that he was convinced a stranger had invaded the left region of his body. He would suddenly feel that the left half of his body no longer belonged to him—that the left half of his head, the upper part of his left trunk, and his left arm and leg were divided from the rest of his body. During an episode, the man believed himself to exist only in the right side of his body, although he remained calm and continued to function normally. Most people around him never noticed anything unusual, even if he was giving a lecture.
Patient 2 was a 30-year-old man suffering from epilepsy that resisted medication. Since age 11 the man experienced seizures characterized by an overwhelming sense of numbness in his legs, chest and neck. The numbness consistently became so intense that he lost awareness of everything below his chin, felt his head was detached from the rest of his body and experienced himself as simultaneously an observer of his body and the subject of observation.
"Clinical observations of disorders like these are very rare," says Olaf Blanke, a neurologist and cognitive neuroscientist at the Brain-Mind Institute (B.M.I.) and a co-author of the paper. "It's difficult even for a novelist or a fiction writer to come up with this."
Heydrich says that these patients provide new clinical evidence for the idea that bodily self-consciousness has three major components: self-location (where in physical space we experience ourselves to be located); first-person perspective (our primary viewpoint of the outside world from a place within the body); and self-identification (the degree to which we feel our bodies are part of us).
An out-of-body experience, Heydrich explains, warps all three aspects of bodily self-consciousness. In contrast, the two patients in the new study maintained normal self-location and first-person perspective even during an illusion. "They still perceived the world from their normal perspective, and they still felt they were in their bodies. But they had strong problem of self-identification. Patient 1 felt that…[the left]…half of him was a stranger and patient 2 felt that everything below his chin was no longer his."
Individuals who have trouble with only one aspect of bodily self-consciousness suggest that the three aspects can be dissociated, offering researchers an opportunity to determine which brain regions or networks underlie which components of self-perception.
An MRI revealed that patient 1 had a brain lesion in the right posterior intraparietal sulcus. In patient 2's brain, the researchers identified a concentration of aberrant electrical activity (the epileptogenic focus) in the right supplementary motor area (SMA) and right superior frontal gyrus. Surgery that removed patient 2's SMA and parts of his superior frontal gyrus cured the seizures and strange bodily perceptions, according to a checkup 15 months later. Heydrich says this implicates the SMA and premotor cortex specifically in the self-identification component of bodily self-consciousness.
"What we found is that the damage in these patients is different than what we find in other illusions, like full-body illusions," Blanke says. "We found damage in high-level motor cortex areas and in the intraparietal sulcus region—both are very multisensory regions," possibly explaining why they are implicated in the sense of self, which integrates many different bodily inputs.
Peter Brugger, a neuropsychologist at University Hospital in Zurich, is cautious about linking specific brain regions to particular kinds of self-perception. "If you operate in a certain region and observe a subsequent change in the behavior, you are very much seduced to think that the behavior resides in this location," Brugger says. "But because the brain primarily consists of connections, you have to think about whether you disrupted some kind of communication or cut faulty connections, not just a region."
Brugger agrees, however, that researchers need to pursue similar studies to better understand bodily self-consciousness. "We can learn and should learn much more from disturbances of bodily perceptions," he says.
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Add CommentIf you think about a particular body part, your consciousness seems to temporially locate or become that member. Otherwise we gather sensory data for innumerable living cells functions. light stimulates the brain activities keeping our eyes open until the brain must shut down to sleep. We eat sleep breathe hurt because we are controlled by tiny living processes inside our body. In this sense we have no consciousness or individualized personal existing self, without having delusional egotistical ignorance
Reply | Report Abuse | Link to this"...bodily self-consciousness has three major components: self-location (where in physical space we experience ourselves to be located); first-person perspective (our primary viewpoint of the outside world from a place within the body); and self-identification (the degree to which we feel our bodies are part of us)."
Reply | Report Abuse | Link to thisThese definitions should be more accurately stated by using terms which identify the context in which they are being used to prevent causing confusion with other, similar, terms. Specifically, the third major component should read, 'physical self-identification' because, 'self-identification' is a much broader concept than what is being referred to here.
". . . bodily self-consciousness has three major components: self-location (where in physical space we experience ourselves to be located); first-person perspective (our primary viewpoint of the outside world from a place within the body); and self-identification (the degree to which we feel our bodies are part of us)."
Reply | Report Abuse | Link to thisThese definitions should be more accurately stated by using terms which identify the context in which they are being used to prevent causing confusion with other, similar, terms. Specifically, the third major component should read, 'physical self-identification' because, 'self-identification' is a much broader concept than what is being referred to here.
Please forgive the double post.
Reply | Report Abuse | Link to this@Baliv,
Reply | Report Abuse | Link to thisThanks for the comment, I was wondering what was specifically meant by "self-identification". I went to the abstract this article links to and it lists the three major components as: "self-location, first-person perspective, and self-location"
Double posts? Happens to all of us. Sometimes I post, and I'm sure I did, but no matter what I try I can see it. I think when this happens the only way to be sure if you posted or not is to close your browser and then open it and go back to the article.
It seems like the non-dominant, pre-motor, cortical attractor space is revealing more and more its essential role in providing the dynamic link between self and other. I discuss this in my Vol.III, 'Neurophilosophy of Consciousness, a BPS Model' but you can see it also in these two articles in my blog:
Reply | Report Abuse | Link to this'Dynamics in Attractor Space' and 'Interspecies Resonant Coupling' http://profiles.yahoo.com/blog/VHN6HSYWK3LTKWCTZZFCKR2C3U Dr.d
These conclusions seem exaggerated and alarmist. "Faulty connections?" Good heavens.
Reply | Report Abuse | Link to thisI've had lots of out of body experiences, mostly while falling asleep--rising up and looking down at myself in the bed. I'll never forget one of them. I flew out a (closed and locked) window and sailed up into the clouds, rolling around and looking down at the town, up at the stars and moon, while wisps of cloud floated by. I could even feel beads of water in the clouds. This adventure probably lasted no more than ten minutes, but it seemed to go on most of the night. What fun! I've also had occasional sensations of someone else being in the room, sometimes getting a pleasant back rub. In my elder years I live alone and no one else was there.
I suspect these are pleasurable dream states or falling asleep daydreams. I've mentioned them to my friends because the episodes are always delightful. (Who doesn't want to fly without visible means of support?)
Nearly all my friends relate their own similar experiences. None of us has epilepsy or other brain problems, we're all intelligent and well-educated, so what's the big deal? When I was a teen I read a book. Can't quite recall the title--something like "Your Amazing Normal Mind". For years I'd had color hearing (synesthesia), "genderizing" of alphabet letters that almost reversed Freud's interpretations, perfect pitch and other amazing normalities mentioned in that book--plus beautiful repetitive dreams and out of body hallucinations which I still have. Reading that book helped me latch on to my synesthesia, realize how beautiful it was (especially for a musician) to see a Dorian mode melody in electric blue, the key of C in bright red, and so on. While I retained color hearing well into middle age I could have shut it off. Many teenagers do. They get worried about being "abnormal" and deliberately discard anything too weird.
That's sad. The human mind wants to be creative while it's asleep or daydreaming as well as when wide awake, so we create our own private, free of charge movies--including out of body experiences. Don't be spooked. "Come fly with me. . ."
This may sound strange, but I feel that conducting further research into the effects of Salvia Divinorum could be very useful in investigating these types of phenomenon. When under the influence of Salvia, I experienced something very similar to patient 1. I felt intense pressure enter most of my body and felt that "I" was located only inside of my index finger, and that somehow the rest of my body was no longer inhabited by my first person conscious experience.
Reply | Report Abuse | Link to thisThe few other times I used the drug I had similar shifts in the perception of where "I" was relation to my body (If I still felt I was inhabiting it). Salvinorin A is a kappa opioid receptor agonist, and causes a strong sense of dissociation or relocation of the self. Perhaps more research into the mechanisms by which Salvinorin A elicits its effects could aid in our understanding of the mechanisms which generate the conscious self.
This may sound strange, but I feel that conducting further research into the effects of Salvia Divinorum could be very useful in investigating these types of phenomenon. When under the influence of Salvia, I experienced something very similar to patient 1. I felt intense pressure enter most of my body and felt that "I" was located only inside of my index finger, and that somehow the rest of my body was no longer inhabited by my first person conscious experience.
Reply | Report Abuse | Link to thisThe few other times I used the drug I had similar shifts in the perception of where "I" was relation to my body (If I still felt I was inhabiting it). Salvinorin A is a kappa opioid receptor agonist, and causes a strong sense of dissociation or relocation of the self. Perhaps more research into the mechanisms by which Salvinorin A elicits its effects could aid in our understanding of the mechanisms which generate the conscious self.
Visualizing Out-of-Body Experience
Reply | Report Abuse | Link to thisin the Brain
Dirk De Ridder, M.D., Ph.D., Koen Van Laere, M.D., Ph.D., D.Sc.,
Patrick Dupont, Ph.D., Tomas Menovsky, M.D., Ph.D.,
and Paul Van de Heyning, M.D., Ph.D.
From the Department of Neurosurgery
and Ear, Nose, and Throat, University Hospital
Antwerp, Antwerp University, Antwerp,
Belgium (D.D.R., T.M., P.V.H.); and
the Department of Nuclear Medicine, University
Hospital Leuven, Leuven, Belgium
(K.V.L., P.D.). Address reprint requests to
Dr. De Ridder at the Department of Neurosurgery,
University Hospital Antwerp,
Wilrijkstraat 10, 2650 Edegem, Belgium,
or at dirk.de.ridder@neurosurgery.be.
N Engl J Med 2007;357:1829-33.
Copyright © 2007 Massachusetts Medical Society.
Summary
An out-of-body experience was repeatedly elicited during stimulation of the posterior
part of the superior temporal gyrus on the right side in a patient in whom
electrodes had been implanted to suppress tinnitus. Positron-emission tomographic
scanning showed brain activation at the temporoparietal junction — more specifically,
at the angular–supramarginal gyrus junction and the superior temporal
gyrus–sulcus on the right side. Activation was also noted at the right precuneus and
posterior thalamus, extending into the superior vermis. We suggest that activation
of these regions is the neural correlate of the disembodiment that is part of the
out-of-body experience.