Researchers offer new theories about memory
June 6, 2003
For decades, scientists have disagreed about the way the brain gathers
memories, developing two apparently contradictory concepts. But newly
published research by a team of scientists at Rutgers-Newark's Center for
Molecular and Behavioral Neuroscience (CMBN) indicates that both models of
memory may be partially correct Î and that resolving this conflict could
lead to new approaches for the treatment of memory disorders such as
Alzheimer's Disease.
The dispute has centered on how the hippocampus Î a structure deep inside
the brain Î processes new information from the senses and stores it. Some
researchers Î such as Mark Gluck and Catherine Myers, co-directors of the
Memory Disorders Project at the CMBN Î have been proponents of "incremental
memory," viewing the acquisition of memory as a learning process that occurs
over time.
"If you see thunder and lightning occur together once, that may be seen
as a coincidence," Myers observed. "But the more often you see them happen
at the same time, the more likely you are to remember them as related parts
of one event."
Other researchers, such as Martijn Meeter, also with the CMBN, have
focused on "episodic memory," which is more like memorization. This model
argues that "an event only has to occur once and you'll remember it," Myers
said. "If someone tells you a name, you may not remember it for a long time,
but you will remember it initially at least." More dramatic events tend to
be stored in long-term memory most easily. But Gluck, Myers and Meeter are
developing a computer model that suggests the two methods of storing memory
work together, and present their novel ideas in a paper published in the
June issue of the journal Trends in Cognitive Science. Research using new
classes of drugs that affect specific portions of a laboratory rat's
hippocampus and the region around it with greater accuracy has led the
Rutgers-Newark team to propose a new interpretation of how the brain
organizes all the sensory input that becomes memories.
That input goes through a kind of assembly line as the brain gathers it
and directs it to the hippocampus, Myers said. Before reaching the
hippocampus itself, the information all passes through a structure adjacent
to the hippocampus called the entorhinal cortex for processing. The two
parts of the brain lie side by side, resembling two halves of a hotdog bun.
The new paper by the Rutgers-Newark investigative team floats the
possibility that the entorhinal cortex Î part of the "hippocampal region"
but not part of the hippocampus itself Î handles incremental learning. The
main task of the hippocampus may be storing episodic memory.
"Understanding how the entorhinal cortex differs in function from the
hippocampus is a hugely important and timely problem in the neurobiology of
memory," Gluck said. "The entorhinal cortex is among the very first brain
regions that are damaged in the earliest stages of Alzheimer's Disease, so
understanding it is crucial to measuring the effectiveness of novel drugs to
fight AD."
Until very recently, write the researchers, only broad generalizations
could be made about how memory was processed in the general hippocampal
region. When humans suffer brain injuries, note the Rutgers-Newark
scientists in their paper, "the damage is seldom limited to a single brain
structure." As a result, some memory functions long assumed to take place in
the hippocampus alone may occur in surrounding parts of the brain, such as
the entorhinal cortex.
A coordinated effort between different portions of the brain, taken as a
whole, may contribute to what we think of as memory, Myers observed. "It's a
team, and everyone is doing a specialized job," she said. She likened much
previous research to the poem The Blind Men and the Elephant, wherein each
of six men is right about the portion of the elephant that he is touching
but is unable to form a comprehensive understanding of the animal as a
whole.
"Everyone has been so caught up in his or her own world that everyone has
been right on one component, but has not been able to take in the larger
picture," Myers said.
Rutgers, the State University of New Jersey
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