Knott Graham, Holtmaat Anthony
Interdisciplinary Center for Electron Microscopy, EPFL, Lausanne, Switzerland.
Brain Res Rev. 2008 Aug;58(2):282-9. doi: 10.1016/j.brainresrev.2008.01.002. Epub 2008 Mar 19.
Changes in sensory experience modify the function of the adult brain's neuronal circuits. This flexibility is reliant on the neurons' ability to change the strength of their connections. Most excitatory connections in the adult cerebral cortex are found on dendritic spines, protrusions from the dendrite that in vitro, and histological analyses, have been shown to be implicated in neuronal plasticity. The recent development of in vivo imaging techniques now provides the ability to explore experience-dependent structural plasticity in the adult brain; the changes in neuronal connectivity that accompany functional reorganizations of the sensory maps. Multi-photon laser scanning microscopy in transgenic mice expressing fluorescent proteins in cortical neurons shows that although the majority of spines is present throughout the imaging period of weeks a proportion of spines is transient, appearing and disappearing on a daily basis. A small fraction appears and stabilizes forming synapses, and this proportion can be affected by changes in sensory experience. This synapse formation occurs preferentially through the initial generation of a filopodial-like spine contacting an axonal bouton already present in the neuropil. The results implicate these specialized compartments of synaptic transmission as playing a central role in the functional reorganization of neuronal circuits.
感觉体验的变化会改变成人大脑神经元回路的功能。这种灵活性依赖于神经元改变其连接强度的能力。成人大脑皮质中的大多数兴奋性连接位于树突棘上，树突棘是从树突伸出的突起，在体外和组织学分析中已被证明与神经元可塑性有关。体内成像技术的最新发展现在提供了探索成人大脑依赖于经验的结构可塑性的能力；即伴随感觉图谱功能重组的神经元连接变化。在皮质神经元中表达荧光蛋白的转基因小鼠中进行的多光子激光扫描显微镜检查表明，尽管在数周的成像期内大多数树突棘都存在，但仍有一部分树突棘是短暂的，每天都会出现和消失。一小部分出现并稳定下来形成突触，并且这一比例会受到感觉体验变化的影响。这种突触形成优先通过最初产生丝状伪足样树突棘来实现，该树突棘与神经毡中已存在的轴突终扣接触。这些结果表明，这些突触传递的特殊区域在神经元回路的功能重组中起着核心作用。
