Sunday, June 6, 2010

Research into cognition explains some age-related memory loss

You really can't teach an old dog new tricks. Well, not if you expect the dog to remember the trick.

Through research into cognitive decline, scientists have demonstrated that "there is a biological reason why people cannot learn new things at an older age, but can retain knowledge learned years before," says John Morrison, dean of basic sciences and the graduate school of biological sciences at Mount Sinai School of Medicine.

Certain types of specializations on nerve cells called "spines" are depleted as someone ages, causing cognitive decline in the part of the brain mediating the highest levels of learning, he explains in a study published June 2 in the Journal of Neuroscience.

We lose certain spines as we age, but this study explains which ones and how their loss impacts cognition--which may lead scientists to develop new therapies that target age-related cognitive decline.

The research team studied six young adult and nine older rhesus monkeys as they participated in a delayed response test. The monkeys watched as food was baited and hidden. Then a screen was put in front of them so they could no longer see the location of the hidden reward. At the beginning of the test, the screen was raised immediately, and the monkeys found the reward right away. The memory of the monkeys was tested by increasing the time the reward was blocked from view. The aged monkeys performed significantly worse on the tests than young monkeys, especially as the time intervals increased, researchers reported.

They then studied the microscopic changes in the nerve cells within the prefrontal cortex, an area of the brain that mediates high level learning. Nerve cells in this area contain both thin, dynamic spines which are key to learning new things, as well as large, mushroom-shaped spines that likely mediate long-term memories and expertise. The older monkeys lacked the thin spines but retained the larger spines, "indicating that the loss of the thin spines may be responsible for monkeys' inability to learn and retain information during the test," says a news release from Mount Sinai.

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