Abstract:

Abnormal Functional Integration of Brain in Depression Evidences from Effective Connectivity Abstract: Functional magnetic resonance imaging (fMRI) is currently the mainstay of neuroimaging in cognitive neuroscience, which could use to understand how different parts of the brain respond to external stimuli by measuring signal changes in the brain. It has a wide range of applications in clinical diagnosis, such as depression disorders. Although depression disorders place an enormous burden on society, and ranked as the fourth leading cause of burden among all diseases, until recently the pathogenesis of depression is not clear. On the one hand, depression is often accompanied with many brain regions or systems abnormality, rather than single region damage. On the other hand, as a nonlinear dynamic system, the human brain is affected by multi-factors, and there are interactions between brain regions, which mask it difficult to understand the complex cognitive process of the brain. So using the method of function integration to dynamic monitor the interaction of multiple brain regions might reveal the pathophysiological mechanism of depression. With the development of the function integration, it has become able to explore the functional brain integration of multiple brain regions, and deeply understand the dynamic mode of the human brain, which represents an important direction of the cognitive neuroscience in the current and future. Functional integration mainly include functional connectivity and effective connectivity. Functional connectivity describes the temporal correlations between spatially remote neurophysiological events, but this method couldn’t reveal the direction of the connection between brain regions; while, effective connectivity mainly reflects the influence one neural system exerts over another, meanwhile, it could reflect how the experimental conditions influence the interaction between the brain regions. That is to say, effective connectivity can describe the dynamic interaction between the brain regions. The main methods of effective connectivity include structural equation model, dynamic causal model, granger causality analysis, psychophysiological interaction and so on. Major depression is characterized by an attentional bias: disproportionately allocate their attention to threatening stimuli and negative memories. Attention bias is accompanied by abnormal connection between the cognitive control system (e.g., DLPFC) and the limbic system (e.g., amygdala). However, it is not yet clear whether this bias represents impaired top-down cognitive control over affective responses, potentially linked to deficits in DLPFC; or enhanced bottom-up responses to affectively laden stimuli that disturb cognitive control mechanisms, potentially linked to deficits in amygdala. By using the methods of effective connection, we can better understanding the dynamic change of these two systems, and provide an effective and specific treatment method for depression. Effective connectivity can be understood from following respects: 1) the concept of the effective connectivity and the necessity of effective connectivity studies; 2) introduction the methods of effective connectivity, including the principles, main contributors, their advantages and drawbacks; 3) the applications to depression; 4) the limitations of the previous studies and the direction for future studies. In the future, effective connectivity will be widely used in basic research and clinical applications, particularly in neural pathway of the diseases and would highly enrich our knowledge about the dynamic integration of the brain regions.

摘要：

摘 要：抑郁症是一种常见的精神障碍。从疾病负担看，目前抑郁症已经成为世界第四大疾病，患病人数呈逐年上升的态势，给家庭和社会带来了沉重的负担。以往大多数对抑郁症的研究关注的是单个脑区结构或功能的损伤，而抑郁症通常伴随多脑区、多系统的异常，而不是单一脑区的损伤。近年来研究者开始关注抑郁症多个脑区之间的功能整合。利用功能整合的方法，动态监测抑郁症多个脑区间的相互作用，能进一步揭示抑郁症的脑网络机制。功能整合的研究方法主要包括功能连接和有效连接。有效连接刻画的是两个（或多个）脑区之间相互作用的因果关系，主要包括结构方程模型、动态因果模型、Granger 因果分析、生理心理交互作用等方法。通过对新近研究的梳理，总体而言，抑郁症的认知控制系统(如背外侧前额叶)和边缘系统（如杏仁核）的之间的有效连接减弱，即背外侧前额叶对杏仁核的抑制作用减弱，使得杏仁核对负性刺激的反应增强，出现了情绪加工偏差和认知偏差。认知控制系统和边缘系统之间有效连接的减弱能够解释抑郁症执行认知控制任务和情绪任务中的异常表现。