Sawtell Nathaniel B, Bell Curtis C
Neurological Sciences Institute, Oregon Health and Sciences University, Beaverton, OR 97006, USA.
J Physiol Paris. 2008 Jul-Nov;102(4-6):223-32. doi: 10.1016/j.jphysparis.2008.10.009. Epub 2008 Nov 1.
The first central stage of electrosensory processing in fish takes place in structures with local circuitry that resembles the cerebellum. Cerebellum-like structures and the cerebellum itself share common patterns of gene expression and may also share developmental and evolutionary origins. Given these similarities it is natural to ask whether insights gleaned from the study of cerebellum-like structures might be useful for understanding aspects of cerebellar function and vice versa. Work from electrosensory systems has shown that cerebellum-like circuitry acts to generate learned predictions about the sensory consequences of the animals' own behavior through a process of associative plasticity at parallel fiber synapses. Subtraction of these predictions from the actual sensory input serves to highlight unexpected and hence behaviorally relevant features. Learning and prediction are also central to many current ideas regarding the function of the cerebellum itself. The present review draws comparisons between cerebellum-like structures and the cerebellum focusing on the properties and sites of synaptic plasticity in these structures and on connections between plasticity and learning. Examples are drawn mainly from the electrosensory lobe (ELL) of mormyrid fish and from extensive work characterizing the role of the cerebellum in Pavlovian eyelid conditioning and vestibulo-ocular reflex (VOR) modification. Parallels with other cerebellum-like structures, including the gymnotid ELL, the elasmobranch dorsal octavolateral nucleus (DON), and the mammalian dorsal cochlear nucleus (DCN) are also discussed.
鱼类电感觉处理的第一个中枢阶段发生在具有类似于小脑的局部回路的结构中。类小脑结构和小脑本身具有共同的基因表达模式，并且可能也具有共同的发育和进化起源。鉴于这些相似性，自然而然会提出这样的问题：从对类小脑结构的研究中获得的见解是否有助于理解小脑功能的各个方面，反之亦然。来自电感觉系统的研究表明，类小脑回路通过平行纤维突触处的联合可塑性过程，对动物自身行为的感觉后果产生习得性预测。从实际感觉输入中减去这些预测有助于突出意外的、因此与行为相关的特征。学习和预测也是当前许多关于小脑本身功能的观点的核心。本综述比较了类小脑结构和小脑，重点关注这些结构中突触可塑性的特性和部位，以及可塑性与学习之间的联系。例子主要取自裸臀鱼的电感觉叶（ELL），以及大量描述小脑在经典条件反射性眼睑条件反射和前庭眼反射（VOR）调节中的作用的研究。还讨论了与其他类小脑结构的相似之处，包括电鳗的ELL、板鳃亚纲动物的背八外侧核（DON）和哺乳动物的背侧耳蜗核（DCN）。
