Too much stress is bad, but too little brings boredom

Too much stress can make you sick, too little stress can make you bored, but U.S. researchers say the right amount tunes the brain. Daniela Kaufer, associate professor of integrative biology at the University of California, Berkeley, and post-doctoral fellow Elizabeth Kirby uncovered exactly how acute stress -- short-lived, not chronic -- primes the brain for improved performance. In studies on rats, the researchers found significant, but brief stressful events caused stem cells in the brain to proliferate into new nerve cells, when mature two weeks later, improved the rats' mental performance. Neural stem cells are a sort of generic or progenitor brain cell that depending on chemical triggers can mature into neurons, astrocytes -- star-shaped glial cells in the brain and spinal cord -- or other cells in the brain. Kirby subjected rats to an acute but short-lived stress -- immobilization in their cages for a few hours. This led to the stress hormone corticosterone levels to become as high as those from chronic stress, but for only a few hours. The stress doubled the proliferation of new brain cells in the hippocampus, a part of the brain. Two weeks later the stressed rats performed better on a memory test, but not two days after the event. The researchers used special cell labeling techniques to establish that the new nerve cells triggered by the acute stress were the same ones involved in learning new tasks two weeks later, the study said. The findings were published in the online journal eLife.