The right brain and the self 2
- From: "Lance" <LanceGary@xxxxxxxxxxxxx>
- Date: 13 Feb 2006 06:26:41 -0800
Losing control
Chris Frith, a neuroscientist at University College London, has long
wondered why people diagnosed with schizophrenia often experience their
own actions as being controlled by others. A person with this severe
mental disorder may report, for example, that space aliens ordered him
to behave destructively.
Fifteen years ago, Frith thought that schizophrenia robbed people of
the ability to monitor their intentions to act. If their behavior came
as a complete surprise, they might attribute it to external forces.
Frith abandoned that idea after reading neurologists' reports of a
strange condition called anarchic-hand syndrome. Damage to motor areas
on one side of the brain leaves these patients unable to control the
actions of the hand on the opposite side of the body. For example, when
one patient tried to soap a washcloth with his right hand, his left
hand, much to his chagrin, kept putting the soap back in its dish.
Another patient used one hand to remove the other from doorknobs, which
it repeatedly grabbed as he walked by doors.
Despite being unaware of any intention to use a hand in these ways,
anarchic-hand patients don't experience their behavior as controlled by
space aliens or another outside entity-they just try to correct their
wayward hands.
Frith now suspects that anarchic-hand syndrome and schizophrenia's
delusions of being controlled by others share a neural defect that
makes it seem like one's movements occur passively. However, people
with schizophrenia mistakenly perceive the passive movements as having
been intentional.
In support of this possibility, Frith and his colleagues find that when
shown scenes of abstract shapes moving across a computer screen,
patients with schizophrenia, but not mentally healthy volunteers,
attribute good and bad intentions to these shapes. Patients with
schizophrenia may monitor their own actions in excruciating detail for
signs of external control, Frith suggests.
In general, people rarely think about their selves but act as if such
entities must exist. "The normal mark of the self in action is that we
have very little experience of it," Frith says.
Harvard University psychologist Daniel Wegner goes further. Expanding
the view of William James, Wegner argues that the average person's
sense of having a self that consciously controls his or her actions is
an illusion. This controversial proposal builds on an experiment
conducted more than 20 years ago by neurophysiologist Benjamin Libet of
the University of California, San Francisco.
Libet found that although volunteers' conscious decisions to perform a
simple action preceded the action itself, they occurred just after a
distinctive burst of electrical activity in the brain signaled the
person's readiness to move. In other words, people decided to act only
after their brains had unconsciously prepared them to do so.
Wegner has since performed experiments demonstrating the ease with
which people claim personal responsibility for actions that they have
not performed. In one study, participants looked in a mirror at the
movements of an experimenter's arms situated where their own arms would
be. When the arms moved according to another researcher's instructions,
volunteers reported that they had willed the movements.
Feinberg says that these findings offer no reason to write off the self
as a mental mirage.
Waist not
A young woman stands in neuroscientist J. Henrik Ehrsson's laboratory
at London's University College and places her palms on her waist. Cuffs
placed over her wrists begin to vibrate tendons just under the skin,
creating the sensation that her hands are bending inward. At the same
time, the woman feels her waist and hips shrink by several inches to
accommodate the imagined hand movements. Dr. Ehrsson's illusory
instant-waist-loss program lasts only about 30 seconds.
Ehrsson and his coworkers used a brain-imaging machine to measure blood
flow in the brains of 24 people as they experienced this illusion.
Parts of the left parietal cortex, located near the brain's midpoint,
displayed especially intense activity as volunteers felt their waists
contract, the scientists report in the December 2005 PloS Biology.
The greater the parietal response, the more waist shrinkage the
individual reported.
The scientists suspect that the activated parietal areas integrate
sensory information from different body parts, a key step in
constructing an internal image of one's body size and shape. When the
brain receives a message that the hands are bending into the waist, it
adjusts the internal body image accordingly, Ehrsson's team
hypothesizes.
The brain can adjust its internal body map in a matter of minutes, the
experiment demonstrates. Researchers who similarly induced illusions of
expanding fingers came to that same conclusion (SN: 7/30/05, p. 69:
Available to subscribers at
http://www.sciencenews.org/articles/20050730/fob5.asp).
The possibility that the brain can redraw body image in dramatic ways
resonates with neuroscientist Miguel A.L. Nicolelis of Duke University
Medical Center in Durham, N.C., and his colleagues. They've found that
after monkeys learn to alter their brain activity to control a robotic
arm, the animals' brains show the same activity pattern as when they
move their own limbs.
Nicolelis' team reported in 2003 that the researchers had implanted
electrodes in the frontal and parietal lobes of the brains of two
female rhesus monkeys that used a joystick to control a cursor on a
computer screen. That action maneuvered a robotic arm in another room.
The animals gradually learned to modulate their brain signals to
reposition the cursor, without moving a muscle.
Electrode data show that, after training, many neurons that formerly
emitted synchronized signals as the monkeys manually manipulated the
joystick to control the robotic arm also did so when the animals
performed the same task mentally. Those results appeared in the May 11,
2005 Journal of Neuroscience.
The monkeys assimilated into their neural self-images a tool that they
had learned to use proficiently, Nicolelis suggests. Apes and people
possess an even stronger capacity for integrating tools into the
brain's definition of self, in his view. This process may underlie the
acquisition of expertise (SN: 4/12/03, p. 234: Available to subscribers
at http://www.sciencenews.org/articles/20030412/bob10.asp).
"Our brains' representations of our bodies are adaptable enough to
incorporate any tools that we create to interact with the environment,
from a robot appendage to a computer keyboard or a tennis racket,"
Nicolelis says.
Self doubts
Despite the proliferation of such studies, the self's special status in
the brain is far from assured. After reviewing relevant brain imaging
and psychology studies, neuroscientists Seth J. Gillihan and Martha J.
Farah, both of the University of Pennsylvania in Philadelphia, found
little compelling evidence for brain networks devoted solely to
physical or psychological aspects of the self.
At most, work such as Feinberg's with brain-damaged patients indicates
that singular brain networks distinguish between one's limbs and those
of other people, the researchers say. There are also suggestions that
other brain areas foster a sense of control over one's limb movements,
Gillihan and Farah reported in the January 2005 Psychological Bulletin.
Still, much of what we typically think of as "the self" may not be
assignable to brain states or structures, in their view.
Feinberg argues that each of the increasingly complex levels of the
brain-including the brain stem, the limbic system, and the
cortex-contributes to intentional actions and to perceiving meaning
in the world, the main ingredients of an "inner I."
Brain-damaged patients vividly illustrate the self's resiliency,
Feinberg adds. While injury to the right frontal brain transforms some
patients' identities in odd ways, other comparably injured patients
somehow maintain their old selves.
A person's coping style and emotional resources usually influence
responses to right brain damage, according to Feinberg's clinical
observations. For example, one patient, a young man living half a world
away from his family, referred to his paralyzed left arm as his
brother's arm.
Feinberg asked the man what it meant to him to possess his sibling's
arm rather than his own. "It makes me feel good," the man responded, in
a voice choked with emotion. "Having my brother's arm makes me feel
closer to my family."
References:
Ehrsson, H.H., et al. 2005. Neural substrate of body size: Illusory
feeling of shrinking of the waist. PLoS Biology 3(December):e412.
Available at http://dx.doi.org/10.1371/journal.pbio.0030412.
Feinberg, T.D., and J.P. Keenan. 2005. Where in the brain is the self?
Consciousness and Cognition 14(December):647-790. Abstract available at
http://dx.doi.org/10.1016/j.concog.2005.01.002.
Feinberg, T.E. 2001. Altered Egos: How the Brain Creates the Self. New
York: Oxford University Press.
Frith, C. 2005. The self in action: Lessons from delusions of control.
Consciousness and Cognition 14(December):752-770. Abstract available at
http://dx.doi.org/10.1016/j.concog.2005.04.002.
Gillihan, S.J., and M.J. Farah. 2005. Is self special? A critical
review of evidence from experimental psychology and cognitive
neuroscience. Psychological Bulletin 131(January):76-97. Abstract
available at http://content.apa.org/journals/bul/131/1/76.
Heatherton, T.F., C.N. Macrae, and W.M. Kelley. 2004. What the social
brain sciences can tell us about the self. Current Directions in
Psychological Science 13(October):190-193. Abstract available at
http://dx.doi.org/10.1111/j.0963-7214.2004.00305.x.
Lebedev, M.A. . . . and M.A.L. Nicolelis. 2005. Cortical ensemble
adaptation to represent velocity of an artificial actuator controlled
by a brain-machine interface. Journal of Neuroscience 25(May
11):4681-4693. Available at
http://www.jneurosci.org/cgi/content/full/25/19/4681.
Uddin, L.Q., et al. 2005. Self-face recognition activates a
frontoparietal "mirror" network in the right hemisphere: an
event-related fMRI study. NeuroImage 25(April 15):926-935. Abstract
available at http://dx.doi.org/10.1016/j.neuroimage.2004.12.018.
Wegner, D.M. 2003. The mind's best trick: How we experience conscious
will. Trends in Cognitive Sciences 7(February):65-69. Abstract
available at http://dx.doi.org/10.1016/S1364-6613(03)00002-0.
Further Readings:
Bower, B. 2005. Mirror cells' fading spark: Empathy-related neurons may
turn off in autism. Science News 168(Dec. 10):373. Available to
subscribers at http://www.sciencenews.org/articles/20051210/fob5.asp.
______. 2005. Fickle finger's funny feel: Digit illusion modifies touch
perception. Science News 168(July 30):69. Available to subscribers at
http://www.sciencenews.org/articles/20050730/fob5.asp.
______. 2003. The stone masters. Science News 163(April 12):234-236.
Available to subscribers at
http://www.sciencenews.org/articles/20030412/bob10.asp.
Sources:
H. Henrik Ehrsson
Functional Imaging Lab
Wellcome Department of Imaging Neuroscience
12 Queen Square
London WC1N 3BG
United Kingdom
Martha J. Farah
University of Pennsylvania
Center for Cognitive Neuroscience
3720 Walnut Street
Philadelphia, PA 19104
Todd E. Feinberg
Albert Einstein College of Medicine
Beth Israel Medical Center
New York, NY 10003
Chris Frith
Institute of Neurology
Wellcome Department of Imaging Neuroscience
University College London
12 Queen Square
London WC1N 3BG
United Kingdom
Seth J. Gillihan
University of Pennsylvania
Center for Cognitive Neuroscience
3720 Walnut Street
Philadelphia, PA 19104
Todd F. Heatherton
Department of Psychological and Brain Sciences
6207 Moore Hall
Dartmouth College
Hanover, NH 03755
Miguel A.L. Nicolelis
Department of Neurobiology
Duke University Medical Center
Bryan Research Building
Box 3209
Durham, NC 27710
Lucina Q. Uddin
Department of Psychology
University of California, Los Angeles
Box 951563
B627 Franz Hall
Los Angeles, CA 90095
Daniel M. Wegner
Department of Psychology
Harvard University
1470 William James Hall
33 Kirkland Street
Cambridge, MA 02138
From Science News, Vol. 169, No. 6, Feb. 11, 2006, p. 90.
http://www.sciencenews.org/articles/20060211/bob9.asp
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