Horwitz Barry
Brain Imaging and Modeling Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
Neuroimage. 2003 Jun;19(2 Pt 1):466-70. doi: 10.1016/s1053-8119(03)00112-5.
Neurons and neural populations do not function as islands onto themselves. Rather, they interact with other such elements through their afferent and efferent connections in an orchestrated manner so as to enable different sensorimotor and cognitive tasks to be performed. The concept of functional connectivity and the allied notion of effective connectivity were introduced to designate the functional strengths of such interactions. Functional neuroimaging methods, especially PET and fMRI, have been used extensively to evaluate the functional connectivity between different brain regions. After providing a brief historical review of these notions of brain connectivity, I argue that the conceptual formulations of functional and effective connectivity are far from clear. Specifically, the terms functional and effective connectivity are applied to quantities computed on types of functional imaging data (e.g., PET, fMRI, EEG) that vary in spatial, temporal, and other features, using different definitions (even for data of the same modality) and employing different computational algorithms. Until it is understood what each definition means in terms of an underlying neural substrate, comparisons of functional and/or effective connectivity across studies may appear inconsistent and should be performed with great caution.
神经元和神经群体并非独立发挥作用。相反，它们通过传入和传出连接与其他此类元素进行精心编排的交互，从而能够执行不同的感觉运动和认知任务。功能连接的概念以及相关的有效连接概念被引入，以指代此类交互的功能强度。功能神经成像方法，尤其是正电子发射断层扫描（PET）和功能磁共振成像（fMRI），已被广泛用于评估不同脑区之间的功能连接。在对这些脑连接概念进行简要的历史回顾之后，我认为功能连接和有效连接的概念表述远未清晰。具体而言，功能连接和有效连接这两个术语被应用于根据功能成像数据类型（例如PET、fMRI、脑电图）计算出的量，这些数据在空间、时间和其他特征方面存在差异，使用不同的定义（即使对于相同模态的数据）并采用不同的计算算法。在尚未理解每个定义在潜在神经基质方面的含义之前，跨研究的功能连接和/或有效连接比较可能显得不一致，并且应该极其谨慎地进行。
