当小鼠处于孤立条件下，海马状突起产生更多的神经干细胞，等待比较好的时期
神经元扫描显微镜图片(图片来自维基共享资源 Nicolasp P. Rougier)
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[The Scientist: June 15, 2011 by Jessica P. Johnson] 哥伦比亚医学中心的研究人员第一次提出证据表明海马状突起(hippocampus)中的神经干细胞的数量可能不是固定的，能够被变化的环境条件所改变，其中海马状突起是大脑中负责记忆、学习和情感的区域。通过比较小鼠暴露在刺激的环境下和在孤立、压力的环境下的海马状突起的变化情况，他们发现那些处在孤立条件下的小鼠海马状突起产生的神经干细胞数量要比处于刺激中的小鼠多，其中这些神经干细胞分化后只能产生神经元。
研究人员提出假设，即在压力或穷乏情况下，大脑通过堆积神经干细胞让自己做好准备，这样它就能适应刺激性较大的环境条件下的要求，因为人们已知刺激的环境能促进更多神经元的产生。这些研究结果，2011年6月9日在线发表在Neuron杂志上，展示了一种新形式的神经可塑性(neural plasticity)。进一步对促进神经元和神经干细胞产生的环境因素和产生的机制进行研究，有可能给患有神经退化性疾病(如阿尔茨海默病和帕金森病)的病人带来新的治疗方法。
Alex Dranovvsky et al., "Experience Dictates Stem Cell Fate in the Adult Hippocampus", Neuron, Volume 70, Issue 5, 908-923, 9 June 2011, doi:10.1016/j.neuron.2011.05.022.
[Abstract]
Adult hippocampal neurogenesis has been implicated in cognitive and emotional processes, as well as in response to antidepressant treatment. However, little is known about how the adult stem cell lineage contributes to hippocampal structure and function and how this process is modulated by the animal's experience. Here we perform an indelible lineage analysis and report that neural stem cells can produce expanding and persisting populations of not only neurons, but also stem cells in the adult hippocampus. Furthermore, the ratio of stem cells to neurons depends on experiences of the animal or the location of the stem cell. Surprisingly, social isolation facilitated accumulation of stem cells, but not neurons. These results show that neural stem cells accumulate in the adult hippocampus and that the stem cell-lineage relationship is under control of anatomic and experiential niches. Our findings suggest that, in the hippocampus, fate specification may act as a form of cellular plasticity for adapting to environmental changes.
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