[tt] [ccm-l] Silent minds

Sat Oct 13 18:09:14 UTC 2007

----- Forwarded message from David Crippen <crippen+ at pitt.edu> -----

From: David Crippen <crippen+ at pitt.edu>
Date: Sat, 13 Oct 2007 11:28:20 -0400
To: ccm-l at ccm-l.org
Subject: [ccm-l] Silent minds

SILENT MINDS
What scanning techniques are revealing about vegetative patients.
by Jerome Groopman
OCTOBER 15, 2007

Ten years ago, Adrian Owen, a young British neuroscientist, was 
working at a brain-imaging center at Addenbrooke's Hospital, at the 
University of Cambridge. He had recently returned from the Montreal 
Neurological Institute, where he used advanced scanning technology to 
map areas of the brain, including those involved in recognizing human 
faces, and he was eager to continue his research. The imaging center 
was next to the hospital's neurological intensive-care unit, and Owen 
heard about a patient there named Kate Bainbridge, a 
twenty-six-year-old schoolteacher who had become comatose after a 
flulike illness, and was eventually diagnosed as being in what 
neurologists call a vegetative state. Owen decided to scan 
Bainbridge's brain. "We were looking for interesting patients to 
study," he told me. "She was the first vegetative patient I came 
across."
For four months, Bainbridge had not spoken or responded to her family 
or her doctors, although her eyes were often open and roving. (A 
person in a coma appears to be asleep and is unaware of even painful 
stimulation; a person in a vegetative state has periods of 
wakefulness but shows no awareness of her environment and does not 
make purposeful movements.) Owen placed Bainbridge in a PET scanner, 
a machine that records changes in metabolism and blood flow in the 
brain, and, on a screen in front of her, projected photographs of 
faces belonging to members of her family, as well as digitally 
distorted images, in which the faces were unrecognizable. Whenever 
pictures of Bainbridge's family flashed on the screen, an area of her 
brain called the fusiform gyrus, which neuroscientists had identified 
as playing a central role in face recognition, lit up on the scan. 
"We were stunned," Owen told me. "The fusiform-gyrus activation in 
her brain was not simply similar to normal; it was exactly the same 
as normal volunteers'."

Excited by this result, Owen resolved to try to conduct brain scans 
of other vegetative patients in the Cambridge area. Since 1997, he 
has studied several dozen people, though he decided to use speech 
sounds rather than photographs to stimulate their brains. (Owen was 
concerned that showing images of faces might not be a reliable way to 
test recognition, since the eyes of vegetative patients often wander. 
"We shifted to auditory responses because you can always put a pair 
of headphones on the person and know that you are transmitting 
sound," he said.) Three years ago, he began using a functional MRI 
(fMRI) scanner, which is faster than a PET scanner, capturing changes 
in blood flow in the brain almost as they occur. The patients' brains 
were scanned while they listened to a recording of simple sentences 
interspersed with meaningless "noise sounds." The scans of some of 
the patients showed the same response to the sentences as scans of 
healthy volunteers, but Owen wasn't sure that the patients had 
understood the words. "So we went the next step up the cognitive 
ladder, to look at comprehension," he said.

Psycholinguists have shown that when we hear a noun at the beginning 
of a sentence we tend to associate the word with its most common 
meaning. For example, Owen said, most people hearing a sentence that 
begins, "The shell was . . ." think of an object typically found at 
the beach. But if the sentence is completed by the phrase "fired at 
the tank," the listener quickly corrects himself, a process that is 
evident on a brain scan. "You can actually see it happening and image 
it on the scanner," Owen said. "The beautiful thing about the 
psychological task is that we just do it automatically. When you play 
ambiguous sentences, areas in the inferior frontal lobe and in the 
posterior temporal lobe become activated, and these areas are very 
important for speech comprehension. They show that you understand the 
meaning of the word: it's not just about perceiving speech; it's 
about decoding. Your brain somehow appreciates that there are two 
meanings to a word like 'shell.' "
Owen eventually identified two vegetative patients whose brains 
showed the same activity in response to ambiguous sentences as the 
brains of healthy volunteers. He also took brain scans of healthy 
physicians, who were presented with the ambiguous sentences while 
under general anesthesia. Owen found that, as the effects of the 
anesthesia increased, the physicians showed less activity in the 
brain regions associated with comprehension. "That, of course, is in 
keeping with our personal experience of consciousness, which is that 
as you sort of drift into sleep you understand less and less of what 
is around you," he said. (An article about this experiment appears 
this week in PNAS, the journal of the National Academy of Sciences.)

Owen's final experiment was the most ambitious: a test to determine 
whether vegetative patients who seemed able to comprehend speech 
could also perform a complex mental task on command. He decided to 
ask them to imagine playing tennis. ("We chose sports, and tried to 
find one that involved a lot of upper-body movements and not too much 
running around," he said.) First, he took brain scans of thirty-four 
healthy volunteers who were instructed to picture themselves playing 
the game for at least thirty seconds. Their brains showed activity in 
a region of the cerebrum that would be stimulated in an actual match. 
"This was an extremely robust activation, and it wasn't difficult to 
tell whether somebody was imagining tennis or not," Owen said. He 
then repeated the experiment using one of the vegetative patients, a 
woman who had been severely injured in a car accident. The woman had 
to be able to hear and understand Owen's instructions, retrieve a 
memory of tennis-including a conception of forehand and backhand and 
how the ball and the racquet meet-and focus her attention for at 
least thirty seconds. To Owen's astonishment, she passed the test. 
"Lo and behold, she produced a beautiful activation, 
indistinguishable from those of the group of normal volunteers," he 
said. (Another vegetative patient, a man in his twenties, also passed 
the test, though Owen, having learned that the man was a soccer fan, 
asked him to imagine playing that sport instead of tennis.)
-- 
David Crippen, MD, FCCM
Associate Professor
University of Pittsburgh Medical Center
Department of Critical Care Medicine
Medical Director- Neurovascular Critical Care
Presbyterian -University Hospital
644a Scaife Hall
3550 Terrace Ave
Pittsburgh, Pa 15261
Administrative Assistant: Barb Shields-  412 647 5387

"Whose motorcycle is this?
It's not a motorcycle....It's a chopper, baby.
Whose chopper is this?
It's Zed's.
Who's Zed?
Zed's dead, baby".

                   Butch

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