Even A Brief Period Of Stress Could Affect Memory: Study

Aside from memory loss, the hippocampus or ‘memory center’ in the brains of rats shrank after just three days of chronic stress.

AsianScientist (Aug. 2, 2016) – An international research team has shown that even a brief period of stress can cause the hippocampus in the brain to start shrinking. Their findings have been published in Scientific Reports.

The hippocampus, considered the memory center of the brain, is made up of a pair of curved structures at the base of our brains and encodes memories of facts and events—names, phone numbers, dates and daily events—that we need to run our lives. This shrinking of the hippocampus precedes the onset of a change in behavior—namely, the loss of memory.

“Until now, no one actually knew the evolution of these changes. Does the hippocampus shrink before or after memory loss? Or do the two happen hand-in-hand?” asked Professor Sumantra Chattarji from the National Center for Biological Sciences in India, who was one of the main investigators of this study.

To address this question, the researchers studied what happens when rats are stressed. Rats react to stress much as humans do: they develop anxiety-related behaviors and their ability to form memories are affected. In a study where the rats were subjected to stress for two hours every day over ten days, striking results emerged after just three days—the hippocampus of every stressed rat had shrunk.

Five days after stress exposure, the rats’ hippocampus-based ability to make memories was tested. Surprisingly, stressed rats performed almost as well as unstressed rats in memory tests, even though volume loss and shrinkage had already happened. At the end of the chronic stress regime, the hippocampus of stressed rats had shrunk even more. In a second and different memory test, the stressed rats performed more poorly compared to unstressed rats.

“Right now, we don’t really know the functional significance of this. There is some evidence that in mice undergoing social stress, only the left hippocampus shrinks,” said PhD student Mr. Mostafizur Rahman, the first author of the study. “If there is any inherent difference between the left and right hippocampus, that needs to be studied.”

The article can be found at: Rahman et al. (2016) Early Hippocampal Volume Loss as a Marker of Eventual Memory Deficits Caused by Repeated Stress.


Source: National Center for Biological Sciences; Photo: Shutterstock.
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