White Edward L
Department of Morphology, Faculty of Health Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer Sheva, Israel.
J Neurocytol. 2002 Mar-Jun;31(3-5):195-202. doi: 10.1023/a:1024109606722.
This report traces the historical development of concepts regarding the specificity of synaptic connectivity in the cerebral cortex as viewed primarily from the perspective of electron microscopy. The occurrence of stereotypical patterns of connection (e.g., contrasting synaptic patterns on the surfaces of spiny vs. non-spiny neurons, the general consistency with which axonal pathways impinge on and originate within specific cortical areas and layers, triadic synaptic relationships) implies that cortical connectivity is highly structured. The high degree of order characterizing many aspects of cortical organization is mirrored by an equally ordered arrangement of synaptic connections between specific types of neurons. This observation is based on quantitative electron microscopic studies of synapses between identified neurons and from the results of correlative anatomical/electrophysiological investigations. The recognition of recurring synaptic patterns and responses between specific neurons has generated increased support for the notion of specificity of synaptic connections at the expense of randomness, but the role of specificity in cortical function is an unresolved question. At the core of cortical processing lie myriad possibilities for computation provided by the wealth of synaptic connections involving each cortical neuron. Specificity, by limiting possibilities for connection, can impose an order on synaptic interactions even as processes of dynamic selection or synaptic remodeling ensure the constant formation and dissolution of cortical circuits. These operations make maximal use of the richness of cortical synaptic connections to produce a highly flexible system, irrespective of the degree of randomness or specificity that obtains for cortical wiring at any particular time.
本报告主要从电子显微镜的角度追溯了关于大脑皮质中突触连接特异性概念的历史发展。典型连接模式的出现（例如，棘状神经元与非棘状神经元表面突触模式的对比、轴突通路与特定皮质区域和层的撞击及起源的总体一致性、三联突触关系）意味着皮质连接具有高度的结构性。皮质组织许多方面的高度有序性反映在特定类型神经元之间同样有序的突触连接排列上。这一观察结果基于对已识别神经元之间突触的定量电子显微镜研究以及相关解剖学/电生理学研究的结果。对特定神经元之间反复出现的突触模式和反应的认识，使得对突触连接特异性概念的支持增加，而随机性的概念则受到削弱，但特异性在皮质功能中的作用仍是一个未解决的问题。在皮质处理的核心是由每个皮质神经元丰富的突触连接所提供的无数计算可能性。特异性通过限制连接的可能性，可以为突触相互作用施加一种秩序，即便动态选择或突触重塑过程确保了皮质回路的不断形成和瓦解。这些操作最大限度地利用了皮质突触连接的丰富性，以产生一个高度灵活的系统，而不管在任何特定时间皮质布线的随机程度或特异性程度如何。
