最新研究：短暂的压力感能增强人的记忆力

据国外媒体报道，尽管长期的压力会增加心脏病发作的风险，并损害到人的免疫系统，但研究人员发现，短暂的压力能提高人的记忆力。

之前的研究表明，慢性压力会提高压力激素水平，压力激素抑制海马体（大脑中被认为是感情和记忆中心的部分）中新神经元的产生，从而损害到记忆。研究还发现，压力激素水平长期升高会增加肥胖、心脏疾病和抑郁症的风险。

而最新在对老鼠的研究中，研究人员发现，显著但短暂的压力事件会使老鼠大脑中干细胞变成新的神经细胞，两个星期后，受到压力的老鼠记忆测试中表现较好。

加州大学综合生物学副教授丹妮拉-考费尔（Daniela Kaufer）表示："从生存方面来说，神经细胞增殖在受到压力后并不能立即帮助你，因为细胞需要时间变得成熟，成为功能神经元细胞。但是，在自然的环境中，急性应激会定期发生，会使保持动物对威胁会更警觉，更适应环境。"

考费尔表示：“大家总是认为压力是个非常不好的东西，其实并不是这样的。一定量的压力对人的身体是有益的，会使人的警觉、行为和认知表现进入最佳水平。我认为间歇性的紧张事件可能使大脑更加警惕，当人处于警觉状态时，往往会有更好的表现。”

不过，研究人员同时指出，受到急性的、激烈的压力有时也是有害的，例如，可能会导致创伤后应激障碍。

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Why some stress is good for you? Acute stress primes the brain to do better on memory tasks two weeks later

"You always think about stress as a really bad thing, but it's not," said Daniela Kaufer, associate professor of integrative biology at the University of California, Berkeley. "Some amounts of stress are good to push you just to the level of optimal alertness, behavioral and cognitive performance." New research by Kaufer and UC Berkeley post-doctoral fellow Elizabeth Kirby has uncovered exactly how acute stress – short-lived, not chronic – primes the brain for improved performance. In studies on rats, they found that significant, but brief stressful events caused stem cells in their brains to proliferate into new nerve cells that, when mature two weeks later, improved the rats' mental performance. "I think intermittent stressful events are probably what keeps the brain more alert, and you perform better when you are alert," she said. Kaufer, Kirby and their colleagues in UC Berkeley's Helen Wills Neuroscience Institute describe their results in a paper published April 16 in the new open access online journal eLife. The UC Berkeley researchers' findings, "in general, reinforce the notion that stress hormones help an animal adapt - after all, remembering the place where something stressful happened is beneficial to deal with future situations in the same place," said Bruce McEwen, head of the Harold and Margaret Milliken Hatch Laboratory of Neuroendocrinology at The Rockefeller University, who was not involved in the study. Brain cells called astrocytes (pink) appear to be key players in the response to acute stress. Stress hormones stimulate astrocytes to release fibroblast growth factor 2 (green), which in turn lead to new neurons (blue). Credit: Daniela Kaufer & Liz Kirby Kaufer is especially interested in how both acute and chronic stress affect memory, and since the brain's hippocampus is critical to memory, she and her colleagues focused on the effects of stress on neural stem cells in the hippocampus of the adult rat brain. Neural stem cells are a sort of generic or progenitor brain cell that, depending on chemical triggers, can mature into neurons, astrocytes or other cells in the brain. The dentate gyrus of the hippocampus is one of only two areas in the brain that generate new brain cells in adults, and is highly sensitive to glucocorticoid stress hormones, Kaufer said.





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