Ozol K O, Hawkes R
Department of Anatomy and Neuroscience Research Group, Faculty of Medicine, University of Calgary, Alberta, Canada.
Histol Histopathol. 1997 Jan;12(1):171-84.
Numerous studies have demonstrated that the cerebellum is highly compartmentalized. In most cases, compartmentation involves the Purkinje cells and the molecular layer, but there is also substantial evidence that the granular layer is subdivided into a large number of highly reproducible modules. We first review the evidence for a modular granular layer. Compartmentation of the granular layer has been revealed both functionally and structurally. First, tactile receptive field mapping has revealed numerous discrete functional modules within the granular layer. The molecular correlates of the receptive fields may be the compartments revealed by histological staining of the cerebellum for several enzymes and antigens. The structural substrate of the receptive fields is the mossy fiber afferent projection map, and anterograde tracing of various mossy fiber projections shows afferent terminals in parasagittal bands within the granular layer that are topographically aligned with the Purkinje cell compartments. Based on this evidence we argue that the cerebellum consists of many hundreds of reproducible structural/functional modules, and that a modular organization is a prerequisite for the efficient parallel processing of information during motor control. The complex organization of the adult granular layer implies elaborate developmental mechanisms. In the second part of the review we consider five developmental models to generate the modular organization of the adult granular layer: 1) the external granular layer is heterogeneous, and its topography translates directly into a modular granular layer; 2) granular layer modules are clones, derived from single external granular layer precursors; 3) modules in the granular layers are a secondary epigenetic response to the compartmentation of the Purkinje cells; 4) modules are secondary to the compartmentation of the afferent terminal fields; 5) modules are sculpted by activity-dependent processes.
大量研究表明，小脑具有高度的分区性。在大多数情况下，分区涉及浦肯野细胞和分子层，但也有大量证据表明颗粒层可细分为大量高度可重复的模块。我们首先回顾支持颗粒层模块化的证据。颗粒层的分区已在功能和结构上得到揭示。首先，触觉感受野映射揭示了颗粒层内众多离散的功能模块。感受野的分子相关物可能是通过对小脑进行几种酶和抗原的组织学染色所揭示的分区。感受野的结构基础是苔藓纤维传入投射图谱，对各种苔藓纤维投射的顺行追踪显示颗粒层内矢状旁带中的传入终末，这些终末在地形上与浦肯野细胞分区对齐。基于这些证据，我们认为小脑由数百个可重复的结构/功能模块组成，并且模块化组织是运动控制期间信息高效并行处理的先决条件。成年颗粒层的复杂组织意味着精细的发育机制。在综述的第二部分，我们考虑了五种发育模型来生成成年颗粒层的模块化组织：1）外颗粒层是异质的，其地形直接转化为模块化颗粒层；2）颗粒层模块是克隆体，源自单个外颗粒层前体；3）颗粒层中的模块是对浦肯野细胞分区的继发性表观遗传反应；4）模块是传入终末场分区的继发性结果；5）模块是由活动依赖过程塑造的。
