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Nature:神经回路的经验学习研究

来源:Nature 2009-01-19 09:00

专题:Nature报道

早期经历能提高大脑适应未来类似事件的能力,这是常识,但最初的经历是怎样在神经回路中表达的、或者说它对再学习有何贡献却不清楚。实验鼠一只眼睛的临时闭合这样一个模型为研究这些问题提供了一个体系。新的经历(即单眼视觉)诱导来自视觉皮层中神经细胞的树突棘的生长。

通过交替单眼视觉和双眼视觉的时间段以及对神经细胞的形态进行几天时间的跟踪,Hofer等人得以能够记录到由经历所诱导的结构变化,并发现它们的持续时间是否能够超过经历本身。他们发现,长寿命的树突棘密度随单眼视觉的丧失而增加,其持续时间超过经历的持续时间。随后再使视觉丧失却未能诱导树突棘密度进一步增加,说明最初经历可能会提供一个结构性经历的“踪迹”,该“踪迹”在对进一步的功能性变化做出反应时可被利用。(生物谷Bioon.com)

生物谷推荐原始出处:

Nature 457, 313-317 (15 January 2009) | doi:10.1038/nature07487

Experience leaves a lasting structural trace in cortical circuits

Sonja B. Hofer1,2, Thomas D. Mrsic-Flogel1,2, Tobias Bonhoeffer1 & Mark Hübener1

1 Max Planck Institute of Neurobiology, D-82152 Martinsried, Germany
2 Present address: Department of Physiology, University College London, London WC1 6JJ, UK.

Sensory experiences exert a powerful influence on the function and future performance of neuronal circuits in the mammalian neocortex1, 2, 3. Restructuring of synaptic connections is believed to be one mechanism by which cortical circuits store information about the sensory world4, 5. Excitatory synaptic structures, such as dendritic spines, are dynamic entities6, 7, 8 that remain sensitive to alteration of sensory input throughout life6, 9. It remains unclear, however, whether structural changes at the level of dendritic spines can outlast the original experience and thereby provide a morphological basis for long-term information storage. Here we follow spine dynamics on apical dendrites of pyramidal neurons in functionally defined regions of adult mouse visual cortex during plasticity of eye-specific responses induced by repeated closure of one eye (monocular deprivation). The first monocular deprivation episode doubled the rate of spine formation, thereby increasing spine density. This effect was specific to layer-5 cells located in binocular cortex, where most neurons increase their responsiveness to the non-deprived eye3, 10. Restoring binocular vision returned spine dynamics to baseline levels, but absolute spine density remained elevated and many monocular deprivation-induced spines persisted during this period of functional recovery. However, spine addition did not increase again when the same eye was closed for a second time. This absence of structural plasticity stands out against the robust changes of eye-specific responses that occur even faster after repeated deprivation3. Thus, spines added during the first monocular deprivation experience may provide a structural basis for subsequent functional shifts. These results provide a strong link between functional plasticity and specific synaptic rearrangements, revealing a mechanism of how prior experiences could be stored in cortical circuits.

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