Nothnagel Nils, Morgan A Tyler, Muckli Lars, Goense Jozien
School of Psychology & Neuroscience, University of Glasgow, Glasgow, United Kingdom.
Functional MRI Facility, National Institute of Mental Health, Bethesda, MD, United States.
Imaging Neurosci (Camb). 2025 Feb 21;3. doi: 10.1162/imag_a_00477. eCollection 2025.
In recent years, ultra-high field functional MRI has allowed researchers to study cortical activity at high spatiotemporal resolution. Advancements in technology have made it possible to perform fMRI of cortical laminae, which is crucial for understanding and mapping of local circuits and overall brain function. Unlike invasive electrophysiology, fMRI provides a non-invasive approach to studying human and animal brain function. However, achieving high spatial resolution has often meant sacrificing temporal resolution. In contrast, line-scanning fMRI maintains both high spatial and temporal resolution, and has been successfully applied to animals to detect laminar differences of the hemodynamic response. Although this method has been extended to human brain imaging in initial studies, staying within SAR safety limits while maintaining a well-defined saturation profile at a short TR is a major challenge. We present a method for gradient-echo-based human line-scanning that uses four saturation regions to achieve a line with narrow FWHM (3.9 mm) at high spatiotemporal resolution (voxel size 0.39 x 3.0 x 3.0 mm, TR = 250 ms). We demonstrate its use for laminar fMRI by measuring laminar time courses in the hand knob of the primary human motor cortex during a finger-tapping task. Our findings indicate differences in the onset and temporal characteristics of the hemodynamic response across cortical layers. Deeper layers exhibited distinct temporal dynamics compared with the gray matter near the cortical surface. Specifically, the BOLD response reached 95% of the maximum amplitude earlier than the superficial layers, and demonstrated a faster return to baseline after stimulus offset. We demonstrate that line-scanning fMRI offers a valuable tool for investigating recordings at a very high temporal and spatial resolution and could help advance our understanding of the mechanistic nature of the BOLD response.
近年来,超高场功能磁共振成像使研究人员能够以高时空分辨率研究皮层活动。技术的进步使得进行皮层分层功能磁共振成像成为可能,这对于理解和绘制局部回路及整体脑功能至关重要。与侵入性电生理学不同,功能磁共振成像提供了一种研究人类和动物脑功能的非侵入性方法。然而,实现高空间分辨率往往意味着牺牲时间分辨率。相比之下,线扫描功能磁共振成像同时保持了高空间和时间分辨率,并已成功应用于动物以检测血流动力学反应的分层差异。尽管该方法在初步研究中已扩展到人类脑成像,但在短重复时间内保持在比吸收率安全限制内并维持明确的饱和分布是一项重大挑战。我们提出了一种基于梯度回波的人类线扫描方法,该方法使用四个饱和区域在高时空分辨率(体素大小0.39×3.0×3.0毫米,重复时间=250毫秒)下实现具有窄半高宽(3.9毫米)的线。我们通过在手指敲击任务期间测量人类初级运动皮层手部旋钮的分层时间过程来证明其在分层功能磁共振成像中的应用。我们的研究结果表明,皮层各层血流动力学反应的起始和时间特征存在差异。与皮层表面附近的灰质相比,更深层表现出明显不同的时间动态。具体而言,血氧水平依赖反应比表层更早达到最大振幅的95%,并在刺激结束后更快恢复到基线。我们证明,线扫描功能磁共振成像为以非常高的时间和空间分辨率研究记录提供了一个有价值的工具,并有助于推进我们对血氧水平依赖反应机制本质的理解。