Chronic Stress Alters the Brain, Affects Memory

University of California Berkeley neuroscientists have discovered evidence that a stress hormone causes stem cells in the brain to produce a white matter cell that may affect memory.

A group of UC Berkeley researchers examined a population of stem cells in the brain’s hippocampus, an area vital to fusing emotion and memory, and a part of the brain that has been known to wither under the effects of prolonged acute stress. Under normal circumstances, the authors note, these cells form new neurons, or glia, a type of white matter.
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The stress hormone cortisol, however, can trip up that programming, and stem cells instead produce an abundance of oligodencrocytes, cells that help coat long fibers of neurons with a type of protective sheath, say the researchers. That sheath, they add, is critical for the transmission of electrochemical signals that are essential to the central nervous system.  

For the study, the authors created stressful situations for rodents, by either immobilizing them for 3 hours a day for 7 days a week, or by injecting them with corticosterone, the rodent equivalent of cortisol in humans.

According to the authors, lab members scooped out the oligodendrocytes from the rodents’ brains, placed them in a dish, added corticosterone, and subsequently took an inventory, finding fewer neurons and a significant increase in oligodencrocytes. And, by blocking corticosterone receptors, the researchers determined the process was tied to the stress hormone.

The study’s findings emphasize that “primary care practitioners should be aware of the differences between the effects of acute and chronic stress on the brain,” says Aaron Friedman, a PhD candidate in the Kaufer Lab, in the department of integrative biology at UC Berkeley, and a study co-author.

In the UC Berkeley study, “we found that chronic stress increases oligodendrogenesis in the rat hippocampus,” continues Friedman. “This suggests that chronic stress, in particular, may lead to structural changes in the brain that will persist even after the stressor ends. So for stress, as with many other health issues, an ounce of prevention may be worth a pound of cure—managing and reducing chronic stress may be an effective approach for preventing stress-induced changes in brain structure that may be very difficult to treat after they have emerged.”

—Mark McGraw

Reference

Chetty S, Friedman A, et al. Stress and glucocorticoids promote oligodendrogenesis in the adult hippocampus. Molecular Psychiatry. 2014.