[tt] NYT: Paul MacLean, 94, Neuroscientist Who Devised Triune Brain Theory, Dies

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Dr. Paul D. MacLean, a neuroscientist and psychiatrist who
developed the intriguing theory of the "triune brain" to explain
its evolution and to try to reconcile rational human behavior
with its more primal and violent side, died on Dec. 26 in
Potomac, Md. He was 94.

Paul MacLean, 94, Neuroscientist Who Devised Triune Brain Theory, Dies
http://www.nytimes.com/2008/01/10/science/10maclean.html

By JEREMY PEARCE

Dr. Paul D. MacLean, a neuroscientist and psychiatrist who
developed the intriguing theory of the "triune brain" to explain
its evolution and to try to reconcile rational human behavior
with its more primal and violent side, died on Dec. 26 in
Potomac, Md. He was 94.

Dr. MacLean's death was confirmed by his family.

In the late 1940s, while he was a young researcher at Yale, Dr.
MacLean became interested in the brain's control of emotion and
behavior. After initial studies of brain activity in epileptic
patients, he turned to cats, monkeys and other models, using
electrodes to stimulate different parts of the brain in conscious
animals. He then recorded the animals' responses and, in the
1950s, began to trace individual behaviors like aggression and
sexual arousal to their physiological sources.

Dr. MacLean (pronounced mac-LANE) termed the brain's center of
emotions the limbic system, and described an area that includes
structures called the hippocampus and amygdala. Developing
observations made by Dr. James W. Papez of Cornell, he proposed
that the limbic system had evolved in early mammals to control
fight-or-flight responses and react to both emotionally
pleasurable and painful sensations. The concept is now broadly
accepted in neuroscience.

Dr. MacLean said that the idea of the limbic system leads to a
recognition that its presence "represents the history of the
evolution of mammals and their distinctive family way of life."

In the 1960s, Dr. MacLean enlarged his theory to address the
human brain's overall structure and divided its evolution into
three parts, an idea that he termed the triune brain. In addition
to identifying the limbic system, he pointed to a more primitive
brain called the R-complex, related to reptiles, which controls
basic functions like muscle movement and breathing. The third
part, the neocortex, controls speech and reasoning and is the
most recent evolutionary arrival.

In Dr. MacLean's theory, all three systems remain in place and in
frequent competition; indeed, their conflicts help explain
extremes in human behavior.

In the 1970s and '80s, aspects of Dr. MacLean's model were
popularized by the astronomer Carl Sagan and the novelist Arthur
Koestler.

The triune brain theory remains controversial. Dr. Thomas R.
Insel, a neuroscientist and director of the National Institute of
Mental Health in Rockville, Md., said the theory was "outside the
mainstream of scientific effort," but added that Dr. MacLean's
research had opened the door for neuroscience to "ask big
questions about consciousness and philosophy, instead of the more
tractable questions about vision and movement."

Paul Donald MacLean was born in Phelps, N.Y. He graduated from
the Taft School and Yale, where he also earned his medical degree
in 1940.

Dr. MacLean was named an assistant professor of psychiatry at
Yale in 1951. He later became an associate professor of
physiology there before moving to the National Institute of
Mental Health in 1957. At the institute, he was chief of the
Laboratory of Brain Evolution and Behavior in Poolesville, Md.,
and retired in the early 1990s.

In 1990, Dr. MacLean explained his theory in a book intended for
specialists, "The Triune Brain in Evolution: Role in
Paleocerebral Functions."

Dr. MacLean's wife of 64 years, the former Alison Stokes, died in
2006. The couple lived in Mitchellville, Md., and on Grindstone
Island, near Clayton, N.Y.

He is survived by a daughter, Alison Cassidy of Potomac; four
sons, Alexander, of Lincoln, Mass.; David, an endocrinologist, of
Middletown, R.I.; James, of Rockville, Md.; and Paul Jr., of
York, N.Y.; a brother, the Rev. Burton MacLean of Pomfret, Conn.;
and 13 grandchildren.

Writing in The New York Times in 1971 and surveying the problem
of intolerance and violence worldwide, Dr. MacLean found that
"language barriers among nations present great obstacles."

"But the greatest language barrier," he concluded, "lies between
man and his animal brains; the neural machinery does not exist
for intercommunication in verbal terms."