WINSTON-SALEM, N.C. - For the first time, a team of Wake Forest University investigators has mapped the functional organization of the hippocampus, the brain's primary memory network, a step that other scientists are calling "a major breakthrough." . The researchers - Sam A, Deadwyler, Ph.D., Robert E. Hampson, Ph.D. and John D. Simeral - report in today's (Dec. 9) Nature that they have mapped the way that a part of the brain, the dorsal hippocampus, encodes information when rats perform a short-term memory task.
The researchers, members of the Department of Physiology and Pharmacology, mapped the actions with an array of 10-16 microelectrodes. The electrodes are small enough to record the electrical impulses of individual brain neurons during the animals' performance. Recordings from the electrodes demonstrate that different portions or segments of the hippocampus are active at different times during the task depending on the type of memory function required.
In the "News and Views" section of the same issue of Nature, Howard Eichenbaum, Ph.D., of the Laboratory of Cognitive Neurobiology at Boston University termed the breakthrough in understanding memory processes highly significant, adding that the study revealed "a functional organization for the hippocampus, one of the highest cortical processing areas in the brain."
The rats are tested in an experimental chamber with two bars or levers positioned on a single wall
as left or right. At the start, only one lever is presented. It is pressed by the animal, then
retracted, followed by a delay period in which the rat must engage in other unrelated activity. The
delay period can be as short as one second or as long as forty seconds -- the rat never knows. At the
end of the delay, both levers appear, and the animal is supposed to press he lever it did not press at
the outset of the trial. If it does, it is rewarded. If the wrong lever is pressed the chamber goes
dark for five seconds and a new
Contact: Robert Conn, Mark Wright or Jim Steele
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Wake Forest University Baptist Medical Center