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） 是研究人脑功能、组织和疾病的核心工具。在这里，我们表明，在静息态和基于任务的扫描期间，基于 fMRI 的功能性大脑连接的估计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失真。我们证明这种伪影是由 fMRI 扫描期间非神经元、全身低频振荡 （sLFO） 血流信号的时间膨胀驱动的，并且不是由标准去噪程序解决的。我们提供的证据表明，sLFO 充气反映了呼吸和心率变化对脑血流的扰动，这些变化伴随着扫描过程中觉醒减少，尽管该途径的机制尚不确定。最后，我们表明，在 fMRI 处理管道中添加专门的 sLFO 去噪程序可以减轻功能连接的人为膨胀，提高 fMRI 结果的有效性和扫描内可靠性。