美国科学家近日首次发现了一种称作“动态连接”（dynamic connectivity）的神经元工作机制，它能帮助大脑更敏锐地感受到外界刺激。这一发现使得科学家能更好地解释为何大脑能快速地区分出刺激的种类。相关论文12月16日在线发表于《自然—神经学》（Nature Neuroscience）上。
当大脑接收刺激信号时，许多神经细胞会同时开启活性，使得大脑无法对信号进行准确识别。这时会产生一种称为侧抑制（lateral inhibition）的现象，即受到刺激的神经细胞会向邻近细胞发出“停火”信号，减低了“噪音”，使得刺激信号能更容易地被鉴别。
在最新的研究中，美国神经认知中心（CNBC）的Nathan Urban和同事仔细研究了大脑嗅球区的侧抑制过程。迄今为止，科学家认为嗅球区的神经连接是固定的，只能进行很缓慢的变化。
然而，研究人员发现，这些连接并不是固定的，它们能根据特定的刺激而发生快速的变化。当大量神经细胞都对刺激作出反应时，这种动态连接使得侧抑制的作用得到加强，过滤了来自其它神经细胞的“噪音”，从而大脑能够清楚地识别出这种刺激，并将其与相似刺激区别开来。
Urban表示，通过理解大脑的工作方式，我们能够将这一机制应用于大脑面临的其它问题上。另外，研究人员还利用计算机将这一大脑机制转化成了一个运算法则——活性依赖侧抑制（ADLI）电脑模型，这使得研究人员能更容易地在大脑其它区域应用这一机制。比如，在一张模糊图片上运用这一模型，能够得到对比强烈的清晰图片（见图片说明）。（科学网 梅进/编译）
原始出处:
Nature Neuroscience
Published online: 16 December 2007 | doi:10.1038/nn2030
Activity-dependent gating of lateral inhibition in the mouse olfactory bulb
Armen C Arevian1,2, Vikrant Kapoor2,3 & Nathaniel N Urban1,2,3
Abstract
Lateral inhibition is a circuit motif found throughout the nervous system that often generates contrast enhancement and center-surround receptive fields. We investigated the functional properties of the circuits mediating lateral inhibition between olfactory bulb principal neurons (mitral cells) in vitro. We found that the lateral inhibition received by mitral cells is gated by postsynaptic firing, such that a minimum threshold of postsynaptic activity is required before effective lateral inhibition is recruited. This dynamic regulation allows the strength of lateral inhibition to be enhanced between cells with correlated activity. Simulations show that this regulation of lateral inhibition causes decorrelation of mitral cell activity that is evoked by similar stimuli, even when stimuli have no clear spatial structure. These results show that this previously unknown mechanism for specifying lateral inhibitory connections allows functional inhibitory connectivity to be dynamically remapped to relevant populations of neurons.
Center for Neuroscience, University of Pittsburgh, A210 Langley Hall, Pittsburgh, Pennsylvania 15260, USA.
Center for the Neural Basis of Cognition, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA.
Department of Biology, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA.
Correspondence to: Nathaniel N Urban1,2,3 e-mail: nurban@cmu.edu
