PNAS：记忆太多太久未必是件好事

为什么有的人能够轻松准确地记住很久以前的事情，却在日常生活中显得很健忘呢？根据美国科学家的最新研究，他们大脑中储存了太多的没用的旧信息，以至于很难迅速地过滤日常的海量信息，并且很难分析和储存短期记忆。通俗地讲，就是“旧的不去，新的不来”。

《美国国家科学院院刊》（PNAS）2016年3月13日发表的这篇文章指出，即使一些看上去很好的事情，比方说大脑中负责学习和记忆的海马区的新的神经元的生长，也就是神经发生（neurogenesis），也未必一定是一件好事。

论文的首席作者之一、哥伦比亚大学医学院的GaelMalleret博士说：“我们吃惊地发现神经生长缓慢可以提高短期记忆，这意味着记得太多未必是一件好事，忘却对于正常的思考和行动是很重要的。”

这与传统的看法相反。很多科学家一直以为海马区的神经生长肯定对记忆有好处。但是Malleret等人提出了相反的假设，并且设计了小鼠模型来测试这一假设。结果他们发现，神经生长被抑制的小鼠比其它小鼠能够能快更好地在迷宫中找到食物。

Malleret说：“总的说来，我们的发现表明海马区的神经元在某些情况下在不同的记忆存储过程中扮演不同的角色。过多的神经生长对一些记忆功能是有害的。”Malleret认为，他们的发现在医疗和人工智能等多个领域具有广泛的意义。

部分英文原文：

Published online before print March 5, 2007, 10.1073/pnas.0611718104

PNAS | March 13, 2007 | vol. 104 | no. 11 | 4642-4646

Paradoxical influence of hippocampal neurogenesis on working memory

Michael D. Saxe*, Gaël Malleret*, Svetlana Vronskaya*, Indira Mendez*, A. Denise Garcia, Michael V. Sofroniew, Eric R. Kandel*,,, and René Hen*,

*Center for Neurobiology and Behavior and Howard Hughes Medical Institute, Columbia University, 722 West 168th Street, New York, NY 10032; and Department of Neurobiology and Brain Research Institute, University of California, Los Angeles, CA 90095

Contributed by Eric R. Kandel, January 3, 2007 (received for review December 18, 2006)

To explore the function of adult hippocampal neurogenesis, we ablated cell proliferation by using two independent and complementary methods: (i) a focal hippocampal irradiation and (ii) an inducible and reversible genetic elimination of neural progenitor cells. Previous studies using these methods found a weakening of contextual fear conditioning but no change in spatial reference memory, suggesting a supportive role for neurogenesis in some, but not all, hippocampal-dependent memory tasks. In the present study, we examined hippocampal-dependent and -independent working memory using different radial maze tasks. Surprisingly, ablating neurogenesis caused an improvement of hippocampal-dependent working memory when repetitive information was presented in a single day. These findings suggest that adult-born cells in the dentate gyrus have different, and in some cases, opposite roles in distinct types of memory.

hippocampus | irradiation | radial maze | interference

Freely available online through the PNAS open access option.