Job Christopher, Tan Seong-Seng
Brain Development Laboratory, Howard Florey Institute, The University of Melbourne, Parkville, Victoria, Australia.
Dev Biol. 2003 May 15;257(2):221-32. doi: 10.1016/s0012-1606(03)00070-8.
The mammalian neocortex is subdivided into regions that are specialised for the processing of particular forms of information. These regions are distinct in terms of their cytoarchitecture, electrophysiology, and connectivity. How this regional diversity is generated through development is currently a topic of considerable interest and has centered upon two main issues. First, to what extent are these regions prespecified by intrinsic genetic mechanisms? Second, what is the influence of extrinsic activity in transmitting signals that ultimately shape functional regions? Historically, experimental evidence has tended to emphasise the role of extrinsic influences, but the identification and analysis of several genes that are expressed asymmetrically in the developing neocortex have tempered this viewpoint. We review current literature from the standpoint that intrinsic influences act early in neocortical development to generate molecular patterning whose main role is the guidance of long-range projections from the dorsal thalamus. Extrinsic influences appear to generate receptive fields for peripheral input, the summation of which determines the areal extent of particular neocortical region.
哺乳动物的新皮层被细分为专门处理特定形式信息的区域。这些区域在细胞结构、电生理学和连接性方面都有所不同。这种区域多样性在发育过程中是如何产生的，目前是一个备受关注的话题，主要集中在两个主要问题上。第一，这些区域在多大程度上由内在遗传机制预先确定？第二，外在活动在传递最终塑造功能区域的信号方面有什么影响？从历史上看，实验证据往往强调外在影响的作用，但在发育中的新皮层中不对称表达的几个基因的鉴定和分析缓和了这种观点。我们从内在影响在新皮层发育早期起作用以产生分子模式的角度来回顾当前的文献，这种分子模式的主要作用是引导来自背侧丘脑的长距离投射。外在影响似乎为外周输入产生感受野，其总和决定了特定新皮层区域的面积范围。
