Functional magnetic resonance imaging (fMRI) is a central tool for investigating human brain function, organization and disease. Here, we show that fMRI-based estimates of functional brain connectivity artifactually inflate at spatially heterogeneous rates during resting-state and task-based scans. This produces false positive connection strength changes and spatial distortion of brain connectivity maps. We demonstrate that this artefact is driven by temporal inflation of the non-neuronal, systemic low-frequency oscillation (sLFO) blood flow signal during fMRI scanning and is not addressed by standard denoising procedures. We provide evidence that sLFO inflation reflects perturbations in cerebral blood flow by respiration and heart rate changes that accompany diminishing arousal during scanning, although the mechanisms of this pathway are uncertain. Finally, we show that adding a specialized sLFO denoising procedure to fMRI processing pipelines mitigates the artifactual inflation of functional connectivity, enhancing the validity and within-scan reliability of fMRI findings.

功能磁共振成像（fMRI）是研究人类大脑功能、组织和疾病的核心工具。在这里，我们表明，基于功能磁共振成像的功能性大脑连接估计在静息状态和基于任务的扫描期间以空间异质速率人为地膨胀。这会产生假阳性连接强度变化和大脑连接图的空间扭曲。我们证明，这种伪影是由 fMRI 扫描期间非神经元、系统性低频振荡 (sLFO) 血流信号的时间膨胀驱动的，并且不能通过标准去噪程序解决。我们提供的证据表明，sLFO 膨胀反映了扫描过程中伴随着觉醒减弱的呼吸和心率变化对脑血流的扰动，尽管该途径的机制尚不确定。最后，我们表明，在 fMRI 处理流程中添加专门的 sLFO 去噪程序可以减轻功能连接的人为膨胀，从而增强 fMRI 结果的有效性和扫描内可靠性。