Nervous System II
structures. Quinlan’s tragic case revealed that the thalamus is also important
in processing thoughts, in providing the awareness and responsiveness that
makes a person a conscious being. In 2005, a similar case arose concerning a
young woman named Terry Schiavo. Many people found the images of her facial
movements on television disturbing. After much debate and discussion, she was
permitted to die. On autopsy, her brain was found to be grossly degenerated.
The cases of Gage, Quinlan, and Schiavo dramatically illustrate the function
of the human brain by revealing what can happen when it is damaged. Nearly
every aspect of our existence depends upon the brain and other parts of the ner-
vous system, from thinking and feeling; to sensing, perceiving, and responding
to the environment; to carrying out vital functions such as breathing and heart-
beat. This chapter describes how the billions of neurons and neuroglia compris-
ing the nervous system interact in ways that enable us to survive and to enjoy
the world around us.
eptember 13, 1848, was a momentous day for Phineas Gage, a
young man who worked in Vermont smoothing out terrain for
railroad tracks. To blast away rock, he would drill a hole, fill it
with gunpowder, cover that with sand, insert a fuse, and then
press down with an iron rod called a tamping iron. The ensuing
explosion would shatter the rock.
On that fateful September day, Gage began pounding on the tamping
iron before his co-worker had put down the sand. The gunpowder exploded
outward, slamming the inch-thick, 40-inch-long iron rod straight through
Gage’s skull. It pierced his brain like an arrow propelled through a soft melon,
shooting out the other side of his head. Remarkably, Gage stood up just a
few moments later, fully conscious and apparently unharmed.
harmed in the freak accident, but in ways so subtle that they
were not at first evident. His friends reported that “Gage was no longer
Gage.” Although retaining his intellect and abilities to move, speak, learn,
and remember, Gage’s personality dramatically changed. Once a trusted,
honest, and dedicated worker, the 25-year-old became irresponsible, shirk-
ing work, cursing, and pursuing what his doctor termed “animal propensi-
ties.” Researchers as long ago as 1868 hypothesized that the tamping iron
had ripped out a part of Gage’s brain controlling personality. In 1994, com-
puter analysis more precisely pinpointed the damage to the famous Gage
brain, which, along with the tamping iron, went to a museum at Harvard
University. Reconstruction of the trajectory of the tamping iron localized two
small areas in the front of the brain that control rational decision-making and
processing of emotion.
More than a hundred years after Gage’s accident, in 1975, 21-year-old
Karen Ann Quinlan drank an alcoholic beverage after taking a prescription
sedative, and her heart and lungs stopped functioning. When found, Quinlan
had no pulse, was not breathing, had dilated pupils, and was unresponsive.
Cardiopulmonary resuscitation restored her pulse, but at the hospital, she
was placed on a ventilator. Within twelve hours, some functions returned—
her pupils constricted, she moved, gagged, grimaced, and even opened her
eyes. Within a few months, she could breathe unaided for short periods.
Quinlan’s responses were random and not purposeful, and she was
apparently unaware of herself and her environment, so she was said to be in
persistent vegetative state.
Her basic life functions were intact, but she had
to be fed and given water intravenously. Fourteen months after Quinlan took
the pills and alcohol, her parents made a request that launched the right-to-
die movement. They asked that Quinlan be taken o±
of life support. Doctors
removed Quinlan’s ventilator, and she lived for nine more years in a nursing
home before dying of infection. She never regained awareness.
Throughout the Quinlan family’s ordeal, researchers tried to fathom
what had happened. A CAT scan performed five years after the accident
showed atrophy in two major brain regions, the cerebrum and the cerebel-
lum. But when researchers analyzed Karen Ann Quinlan’s brain in 1993, they
were surprised. The most severely damaged part of her brain was the thala-
mus, an area thought to function merely as a relay station to higher brain
A rod that blasted through the head of a young railway worker has taught us
much about the biology of personality.
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