胼胝体调节大脑两半球相互作用的机制

胼胝体是哺乳动物脑内最大的白质结构,不仅可以在大脑两半球间传递信息,也能调节半球间的相互作用,“抑制模型”和“兴奋模型”是当前解释胼胝体调节机制的主要模型.前者假设,胼胝体对半球间的信息传递起抑制作用,表现为优势半球的功能增强,非优势半球的活动抑制,因而可以提高半球加工的独立性和功能不对称性；后者则认为,胼胝体对半球间信息传递起促进作用,导致两半球同时性活动,并增强其功能连接性,因而可以降低半球的功能不对称性,有利于半球间的信息共享与功能整合.近期的研究显示,胼胝体并不是一个结构与功能的单一体,而是包含了在空间与时间上既分离又互动的多通道信息加工复合体.抑制与兴奋信息可以通过胼胝体的不同空间通道以不同的速度在半球间进行传递,并受到任务计算类型与复杂性的调节,因此,胼胝体的抑制与兴奋的协同可以调节两半球的动态相互作用.

Mechanisms of Corpus Collosum’s Regulation on Interhemispheric Interactions

The corpus callosum is the largest neural pathway connecting the two cerebral hemispheres in mammals. Not only does it transmit information between the hemispheres, but also regulates interhemispheric information processing. “Inhibitory model” and “excitatory model” are the primary models proposed to explain the regulation mechanisms. The former hypothesized that the corpus callosum could inhibit the transfer of information between the hemispheres, so that the function of the dominant hemisphere was enhanced and the activity of non-dominant hemisphere was suppressed. As a result, the independence of the processing information in each hemisphere and the degree of the cerebral functional lateralization could be increased. In contrast, the latter assumed that the corpus callosum might play an excitatory role in interhemispheric transfer of information. According to the excitatory model, both hemispheres would be activated simultaneously and the interhemispheric connectivity would be strengthened. This mechanism might reduce the cerebral functional asymmetry and facilitate the share and the integration of interhemispheric information. However, some new evidence showed that the corpus callosum is not a single structural and functional body, but consists of multiple information processing channels separating or interacting spatially and temporally. Inhibitory and excitatory information could be transmitted separately between cerebral hemispheres through these different spatial channels at different speeds. Meanwhile, this information transfer might be regulated by task-computing types and task complexity. Therefore, the coordination of inhibition and excitation of the corpus callosum could regulate the dynamic interactions between the two cerebral hemispheres.