New research is helping scientists to understand split personalities, says Raj Persaud

John johnhkm at
Sat Sep 25 23:41:53 EST 1999

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AFTER years of doubt and controversy, multiple personalities have been seen
inhabiting the same brain for the first time in a study conducted by a team
of American scientists.

Using a brain scanner, a group of doctors, led by Prof Guochuan Tsai at
Harvard Medical School, has performed the first in-depth imaging study of
brain activity in multiple personality disorder.

The disorder is one of the most dramatic and controversial diagnoses in
psychiatry and was made famous by books and films such as The Three Faces of
Eve and Sybil (who claimed 16 different personalities). Patients contend
that totally different personalities inhabit their minds and can take over
their bodies from time to time.

These personalities might be of a different sex, age, skill, hand
preference, motivation and emotional style from the usual persona. After a
switch back to the base or core personality, the patient cannot remember the
period during which the other personalities were in control.

The theory is that in the face of some extreme trauma, often childhood
sexual abuse, the mind deals with overwhelming stress by producing an
alternative personality that experiences the shock, so protecting the core
personality, for whom the terrible event never occurred.

But British psychiatrists have always been more sceptical than their
American counterparts. This cynicism follows the use of multiple personality
disorder as a defence in several legal battles over heinous crimes, where
perpetrators complained that another personality in their minds was guilty,
not them.

In the early 1980s, Ken Bianchi, an American serial killer nicknamed the
Hillside Strangler, claimed it was another personality inhabiting his body
who had committed a string of murders. But psychiatrists suspected he was
faking his supposed two personalities, and told him that sufferers usually
have at least three different personalities. Bianchi immediately produced

Bianchi aside, is the phenomenon real? Most British psychiatrists suspect
pretence is at the root of multiple personality disorder.

At Harvard, Dr Tsai's team used functional Magnetic Resonance Imaging to
highlight blood flow in the brain in the hope of revealing the underlying
mechanism of personality switching. They asked each patient to switch to a
third "pretend" personality as a control condition, providing a comparison
for the activity of alternative personalities. The subjects would confirm
the moment of a switch in personality by pressing a button in the scanner.

When a patient was changing from her normal personality to the main
alternative one, part of the brain now thought to code our memories of
significant episodes from our pasts, the hippocampus, seemed to be
inhibited - its activity was significantly decreased. When she switched back
from her "alter" personality to her normal one, the hippocampus was more
active than in the alter personality.

These results throw new light on the science of where our sense of self is
located. The hippocampus is the "antenna" of the brain, attuned to the
environment and sensitive to the stresses of life. Many victims of abuse
have hippocampal degeneration, as did the subject examined by Dr Tsai.
Perhaps a compromised hippocampus is vulnerable to a personality switch.

The work shows that who we are is strongly determined by memories of
significant past events, as one would expect. It might even be that holding
on to past turning points in our lives continues to define our outlook, and
to change our personality we have to alter the focus of our memory of the

These brain-scanning results also converge with the current therapy for
multiple personality disorder. This is to encourage the patient to recall
and perhaps even relive the traumatic early event that first produced the
switch to another personality.

It is striking that when the person is returning from their "alter"
personality to their base, or core, the activation occurs in their right
hippocampus. It is this right side that is hypothesised to be implicated in
more emotional experiences. So it could be that recalling especially
emotional memories is vital to our sense of self, and denying them renders
us prone to forgetting who we really are.

But perhaps the most revolutionary finding in this research is the fact that
a brain structure was identified as a switch of multiple personalities, but
that this switch is not active when the patient is instructed to pretend to
shift to a feigned personality.

This means the new technique of functional MRI brain scanning could begin to
persuade British psychiatry to regard multiple personality disorder as a
brain dysfunction. A redrawing of the map of disorders previously attributed
to malingering and other dubious motivations could now be heralded by this
study. For these brain-scanning techniques allow clinicians to look past the
pretence and directly into the brain.

Dr Raj Persaud is a consultant psychiatrist at the Maudsley
Hospital London
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