撕裂人

二 |     A team of scientists has discovered a likely explanation for why one may feel exhausted after engaging in intense cognitive work.,In their study, published in the Current Biology last week, the researchers argue that intense cognitive work, when it lasts for several hours, results in the buildup of potentially toxic byproducts in the prefrontal cortex part of the human brain, which then affects a person’s behavior.,“Influential theories suggested that fatigue is a sort of illusion cooked up by the brain to make us stop whatever we are doing and turn to a more gratifying activity,” Mathias Pessiglione of Pitié-Salpêtrière University in Paris, said as quoted in a news release by Cell Press. “But our findings show that cognitive work results in a true functional alteration—accumulation of noxious substances—so fatigue would indeed be a signal that makes us stop working but for a different purpose: to preserve the integrity of brain functioning.”,During the course of their research, the team employed magnetic resonance spectroscopy to monitor the brain chemistry of two groups of people during a workday, with one group performing easy cognitive tasks while the other engaged in more complex mental activities.,Only the latter group ended up exhibiting signs of fatigue, as well as a tendency to favor “options proposing rewards at short delay with little effort,” as the news release put it.,AmericasChild Survives After 7 Minutes Without Blood Flow to Brain During Surgery, US Cardiologist Reveals11 August, 16:41 GMT,Furthermore, members of that group had higher levels of glutamate in the synapses of the prefrontal cortex, leading the researchers to suggest that the accumulation of glutamate “makes further activation of the prefrontal cortex more costly,” and thus a mentally exhaustive workday makes cognitive control more difficult.,Unfortunately, there seems to be no fancy way to deal with this problem other than the tried and tested method that is probably as old as history itself.,“I would employ good old recipes: rest and sleep!” Pessiglione remarked. “There is good evidence that glutamate is eliminated from synapses during sleep.”。据悉，从1983年起，《美国新闻与世界报道》杂志开始对美国大学进行年度排名，迄今已有近40年历史，早已成为广大学生和家长择校的重要参考。另据美国《财富》杂志网站报道，根据哥大的数据，目前在哥大就读，本科生一学年的学费为65000美元，加上食宿费，每名学生每年大概花费86000美元（约合人民币60万元），按获得本科学位通常需要四年时间计算，每名本科大学生大概需要花费人民币240万元。据估计，剔除通胀因素后，2020至2021学年，美国私立大学的平均学费比30年前整整翻了一番。

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