Science2014-06-10 4:00 PM

加拿大解密婴儿为什么容易失忆 Hippocampal Neurogenesis Regulates Forgetting During Adulthood and Infancy

论文摘要 

为什么回忆孩提早期的记忆是如此之难?新的研究提示,神经发生——或新的神经元的产生可能在这一“婴儿期失忆”中起着一个显著的作用;婴儿期失忆发生在范围广泛的物种中,其中包括人类。由于神经元为形成新的记忆而不断地在大脑的海马区内产生,研究人员想知道这一新神经元的持续性整合是否可能会重新排布脑内的连接,从而动摇了旧的记忆并引起健忘。Katherine Akers及其同事如今显示,这种现象也会发生在小鼠、豚鼠、以及一种叫做“八齿鼠”的小啮齿类动物中。

研究人员用轻微的电击来训练一组小鼠,使其对某种特定的环境感到害怕。他们接着让那些小鼠中的某些接触转轮,因为转动一直显示能自然地增强神经发生的水平。当Akers及她的同事后来让这些小鼠重新回到它们被训练产生恐惧的环境之时,他们发现,那些有转轮经历的小鼠大体上忘却了它们的恐惧,而没有转轮经历的小鼠似乎能相当好地回忆起近来受到的电击。

研究人员接着用药物来减缓婴儿期小鼠——婴儿期小鼠通常会比成年期小鼠有着更高水平的神经元产出——的神经发生速度并发现,那些小鼠会比它们的未用过药物的对等婴儿期小鼠更好地保留其记忆。Akers和她的同事最后在豚鼠和八齿鼠中测试了神经发生对健忘的影响,这些动物在出生时具有成熟的神经元且在婴儿期没有经历那么多的神经发生。

他们发现,婴儿期的豚鼠及八齿鼠没有婴儿期小鼠那样快速地忘记它们的恐惧--但当研究人员给另外2种动物一种药物以刺激其神经发生时,这些啮齿动物也开始忘却了它们的恐惧。这些结果暗示了婴儿期健忘的基本机制,而一则由Lucas Mongiat和Alejandro Schinder撰写的《观点栏目》文章更为详细地解释了这些发现。

Abstract 

Throughout Life, new neurons are continuously added to the dentate gyrus. As this continuous addition remodels hippocampal circuits, computational models predict that neurogenesis leads to degradation or forgetting of established memories. Consistent with this, increasing neurogenesis after the formation of a memory was sufficient to induce forgetting in adult mICE. By contrast, during infancy, when hippocampal neuroGENEsis levels are high and freshly generated memories tend to be rapidly forgotten (infantile amnesia), decreasing neurogenesis after memory formation mitigated forgetting. In precocial species, including guinea pigs and degus, most granule cells are generated prenatally. Consistent with reduced levels of postnatal hippocampal neurogenesis, infant guinea pigs and degus did not exhibit forgetting. However, increasing neurogenesis after memory formation induced infantile amnesia in these species.

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