通过语言任务和功能磁共振成像研究人类小脑功能

Since the 19th century, people have long believed that the function of cerebellum was restricted to fine motor control and modulation. In the past two decades, however, more and more studies challenged this traditional view. While the neuroanatomy of the cerebellum from cellular to system level has been well documented, the functions of this neural organ remain poorly understood. This study, including three experiments, attempted to further the understanding of cerebellar functions from different viewpoints. Experiment One used the parametric design to control motor effects. The activation in cerebellum was found to be associated with the difficulty levels of a semantic discrimination task, suggesting the involvement of the cerebellum in higher level of language functions. Moreover, activation of the right posterior cerebellum was found to co-vary with that of the frontal cortex. Experiment Two adopted the cue-go paradigm and event-related design to exclude the effects of phonological and semantic factors in a mental writing task. The results showed that bilateral anterior cerebellum and cerebral motor regions were significantly activated during the task and the hemodynamic response of the cerebellum was similar to those of the cerebral motor cortex. These results suggest that the cerebellum participates in motor imagination during orthographic output. Experiment Three investigated the learning process of a verb generation task. While both lateral and vermis cerebellum were found to be activation in the task, each was correlated a separate set of frontal regions. More importantly, activations both in the cerebellum and frontal cortex decreased with the repetition of the task. These results indicate that the cerebellum and frontal cortex is jointly engaged in some functions; each serves as a part of a single functional system. Taken these findings together, the following conclusions can be drawn: 1.The cerebellum is not only involved in functions related to speech or articulation, but also participates in the higher cognitive functions of language. 2.The cerebellum participates in various functions by supporting the corresponding regions in cerebral cortex, but not directly executes the functions as an independent module. 3.The anterior part of cerebellum is related to motor functions, whereas the posterior part is involved in cognitive functions. 4.While the motor functions rely on the engagement of both sides of the cerebellar hemispheres, the higher cognitive functions mainly depend on the right cerebellum.

从19世纪以来，人们长期认为小脑的功能局限于精细运动的控制与调节，然而近20多年的研究不断对这一传统观点提出挑战。在对小脑的结构从宏观到微观都已经有了比较清楚的了解的同时，对其功能的认识却远没有达到相应的水平。 本研究通过三个实验试图从不同侧面加深对小脑功能的认识： 实验一用参数设计排除可能的运动影响，发现右后侧小脑激活与语义辨别的难度相关，提示小脑参与语言的高级认知过程。本实验还观察到小脑与额叶活动的共变关系。 实验二采用心理书写任务，通过线索-启动的事件相关模式排除了语音和语义的干扰，结果显示双侧小脑前部和运动相关的大脑区域显著激活，并且小脑的活动时间特性与运动区相似，提示小脑参与了字形输出过程中的运动想象。 实验三考察动词产生任务的学习过程，发现小脑前外侧部和后内侧部都参与了该任务，并且这两个区域与额叶的关联程度是不同的。随着练习，小脑与额叶的激活共同减弱。这些结果说明小脑与额叶的一些区域构成一个体系。 由上述实验我们得出了如下结论： 1.小脑不仅参与言语运动相关功能，也参与语言的高级认知功能； 2.小脑参与各种功能的方式是支持大脑的相应脑区，而不是完成这些功能的独立模块； 3.小脑前部与运动功能有关，而小脑后部支持认知功能； 4.小脑的运动相关功能是双侧参与的，高级认知相关功能表现为右侧化。