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August 03, 2010
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“Vegetative” patient can think, study suggests
Sept. 11, 2006
Special to World
Science
An outwardly unresponsive
patient diagnosed as being in a vegetative state was capable
of understanding and responding to some instructions in a
new brain-imaging study, according to researchers.
Scientists said the finding suggests consciousness exists in
some patients who were thought to lack it. But they cautioned that
this case might not apply to others because each brain injury is
different.
Nonetheless, they said, it’s a step toward providing information for
families of vegetative and comatose patients worldwide, who wonder daily
whether their injured relative can understand them.
A study published last year found that some nearly comatose patients
classified as being in a “minimally conscious state”
have signs of awareness.
In the new research, Adrian Owen of the Medical Research Council
in Cambridge, U.K. and colleagues used functional Magnetic Resonance
Imaging technology to measure the brain responses of a patient
who was instead in a “persistent vegetative state.”
The 23-year-old woman had suffered a severe traumatic brain injury
in a traffic accident. After an initial coma, she opened her
eyes and showed normal sleep-wake cycles, researchers said. But
she remained “unresponsive” and lacking in “spontaneous,
intentional behaviors,” according to doctors—markers
of a vegetative state. She had been this way for five months at the
time of the study.
Her brain responses to spoken sentences were similar to those of
healthy volunteers, the researchers reported, but these responses
are thought to be relatively automatic and have been elicited
from other unconscious subjects.
Investigating further, the authors asked the patient to imagine
herself playing tennis and visiting all of the rooms in her
house. Again, her brain responses closely matched those of healthy volunteers,
they noted. The findings appear in the Sept. 8 issue of the
research journal Science.
The “findings indicate the existence of a rich mental life,
including auditory language processing and the ability
to perform mental imagery tasks,” wrote Lionel Naccache of
the National Institute for Health and Medical Research in Orsay,
France, in a commentary in the journal.
But Naccache and Owen said it’s important not to generalize
from this single patient to most other vegetative-state patients.
“This is unlikely the case for all vegetative patients.
It’s such a heterogeneous group; they all have brain injuries
of different types,” Owen said.
Functional Magnetic Resonance Imaging, or fMRI, is a system for measuring
blood flow in the brain using radio waves and a strong magnetic
field.
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Homepage image: The brain of a healthy
volunteer scanned by fMRI when the volunteer is asked to think of playing
tennis.
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