Krembil Brain Institute, University Health Network Toronto, Ontario, Canada; Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; Center for Neuroscience Imaging Research, Institute for Basic Science & Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.
Neuroimage. 2023 Aug 15;277:120249. doi: 10.1016/j.neuroimage.2023.120249. Epub 2023 Jun 24.
In this primer, I provide an overview of the physiological processes that contribute to the observed BOLD signal (i.e., the generative biophysical model), including their time course properties within the framework of the physiologically-informed dynamic causal modeling (P-DCM). The BOLD signal is primarily determined by the change in paramagnetic deoxygenated hemoglobin, which results from combination of changes in oxygen metabolism, and cerebral blood flow and volume. Specifically, the physiological origin of the so-called BOLD signal "transients" will be discussed, including the initial overshoot, steady-state activation and the post-stimulus undershoot. I argue that incorrect physiological assumptions in the generative model of the BOLD signal can lead to incorrect inferences pertaining to both local neuronal activity and effective connectivity between brain regions. In addition, I introduce the recent laminar BOLD signal model, which extends P-DCM to cortical depths-resolved BOLD signals, allowing for laminar neuronal activity to be determined using high-resolution fMRI data.
在这个简介中，我提供了对促成观察到的 BOLD 信号的生理过程的概述（即产生生物物理模型），包括在生理启发的动态因果建模（P-DCM）框架内的时程特性。BOLD 信号主要由顺磁性去氧血红蛋白的变化决定，这是由氧代谢、脑血流和体积变化的组合引起的。具体来说，将讨论所谓的 BOLD 信号“瞬态”的生理起源，包括初始过冲、稳态激活和刺激后的下冲。我认为，BOLD 信号产生模型中的不正确生理假设会导致对局部神经元活动和脑区之间有效连接的不正确推断。此外，我介绍了最近的皮层分层 BOLD 信号模型，它将 P-DCM 扩展到皮层深度分辨的 BOLD 信号，允许使用高分辨率 fMRI 数据确定皮层分层神经元活动。
