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Hard- wiring the brain
This news article was taken from the Dallas Times Herald, Wednesday,
November 1, 1989. The article originated from the Los Angeles Times.
SCIENTISTS PROVE BRAIN THEORY
(Computer-like `hard-wiring' allows cells to store memories)
LOS ANGELES - Researchers at the University of Southern
California and the University of Illinois Have for the first time
experimentally confirmed the longstanding theory that the brain stores
memories by "hard-wiring" new connections between groups of brain
cells.
Their results, to be reported today at a meeting of the Society
for Neuroscience in Phoenix, Ariz. are the culmination of decades of
research for the physical mechanisms underlying the mysterious process
by which the brain stores memories.
In two separate sets of experiments involving rats and rabbits,
the researchers clearly identified memory-related changes in the
physical links among groups of brain cells, or neurons. The changes
occurred when the animals learned specific physical activities, such
as blinking an eye in response to the ringing of a bell or learning to
walk along an elevated pathway.
The experiments offer an explanation for why some types of
learned behavior, such as the ability to ride a bicycle, are never
forgotten. The reason is that the necessary muscle commands for
riding a bicycle, for instance, are hard-wired into brain cells in the
same way that some commands for operating a computer are permanently
stored by wiring transistors together.
"In terms of vertebrates, we really haven't had any direct
information about anatomical changes related to specific learning
events," said neuroscientist Lawrence R. Squire of the Veterans
Affairs Hospital in San Diego. "This will greatly increase our level
of certainty" about how memories are formed, he added.
Psychobiologists Richard F. Thompson of USC and William Greenough
of Illinois have been studying a so-called Pavlovian response in
rabbits. The technique is named after Russian physiologist Ivan
Pavlov, who rang a bell every time he fed a group of dogs. After
training, the dogs began to salivate evert time the bell was rung,
even if they were not given food.
Thompson rang a bell every time he directed a mild puff of air
into one eye of rabbits, causing them to blink. After training, the
rabbits would blink every time the bell was rung.
Implanting microelectrodes throughout the brain, Thompson and his
colleagues found that the learned blinking was controlled by a small
group of cells, called Purkinje cells, in the cerebellum, which is the
brain's coordinating center for muscular activity. When they
surgically removed the small group of Purkinje cells, the animals no
longer blinked.
Thompson then turned the trained animals over to Greenough, whose
specialty is looking for signs of increased connections between brain
cells.
Page 1
In previous studies with rats, Greenough had shown that rats
raised in an "enriched" environment - one with lots of toys and other
mentally stimulating objects - have a much greater number of
intercellular connections then those raised in a more sterile
environment. In those cases, however, the increased connections could
not be associated with specific memories.
In the new study, Greenough and his students studied the number
of intercellular connections in the specific area of the cerebellum
that Thompson had shown controlled the eye-blink behavior. They
compared the number of connections in this area to the number on the
opposite side of the cerebellum, controlling the eyelid that was not
trained, and found a significant difference.
In the 15 rabbits studied over a two-year period,
"The differences were statistically reliable and clearly visible,"
Greenough said. "We really have isolated a case where, in brain
cells that are clearly involved in the performance of a task, we
have crystal clear [structural] change that indicated a change in
anatomical circuitry."
The discovery of altered numbers of connections, Thompson added,
"is not surprising, in that it fits theory, but there has been no
particular evidence [to support the theory] before. We were
convinced there would be something like this because memories are
never forgotten."
The cerebellums of all mammals are remarkably similar, Greenough
noted, and researchers are confident that discoveries made in animal
brains are applicable to humans. They also believe that the mechanism
used for storing memories involved with muscle movements will be
similar, if not identical to, those involved in storing other types of
memories.
Thompson noted that the brain has the potential for "trillions
and trillions" of such physical connections, so that the physical
structure of the brain does not limit the number of things that can be
remembered.
Both Thompson and Greenough caution that researchers are only
beginning to unravel the mechanism of memory formation. "This is a
major advance," Greenough said, "but it is only a first step that
leads to a lot more research rather then a last step that wraps
everything up."
{Gee Wiz it's amazing how medical science is advancing! Just
think that maybe they will discover that magnetic energies can
effect the BRAIN !!! }
R.B.
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