Fast fMRI enables the detection of neural dynamics over timescales of hundreds of milliseconds, suggesting it may provide a new avenue for studying subsecond neural processes in the human brain. The magnitudes of these fast fMRI dynamics are far greater than predicted by canonical models of the hemodynamic response. Several studies have established nonlinear properties of the hemodynamic response that have significant implications for fast fMRI. We first review nonlinear properties of the hemodynamic response function that may underlie fast fMRI signals. We then illustrate the breakdown of canonical hemodynamic response models in the context of fast neural dynamics. We will then argue that the canonical hemodynamic response function is not likely to reflect the BOLD response to neuronal activity driven by sparse or naturalistic stimuli or perhaps to spontaneous neuronal fluctuations in the resting state. These properties suggest that fast fMRI is capable of tracking surprisingly fast neuronal dynamics, and we discuss the neuroscientific questions that could be addressed using this approach.

快速功能磁共振成像能够检测数百毫秒时间尺度的神经动力学，这表明它可能为研究人脑亚秒级神经过程提供新途径。这些快速功能磁共振成像动态的幅度远远大于血流动力学响应的典型模型的预测。几项研究已经确定了血流动力学响应的非线性特性，这对快速功能磁共振成像具有重要意义。我们首先回顾了可能构成快速功能磁共振成像信号基础的血流动力学响应函数的非线性特性。然后，我们说明了快速神经动力学背景下典型血流动力学响应模型的分解。然后，我们将论证，典型的血流动力学响应函数不太可能反映对由稀疏或自然刺激驱动的神经元活动或可能对静息状态下的自发神经元波动的 BOLD 响应。这些特性表明快速功能磁共振成像能够跟踪令人惊讶的快速神经元动态，我们讨论了可以使用这种方法解决的神经科学问题。