The primary visual cortex of humans contains patches of neurons responding preferentially to stimulation of one eye (the ocular dominance columns). The majority of previous fMRI studies reporting eye-specific activity in V1 used magnetic field strengths of 4 T and higher. However, there have been reports of reliable eye-selective activations at 3 T as well. In this study we investigated the possibility of detecting eye-selective V1 activity using high-resolution GE-EPI fMRI at 3 Tesla and sub-millimeter resolution fMRI at ultrahigh 9.4 Tesla magnetic field strengths with acquisition parameters optimized for each field strength. High-resolution fMRI at 9.4 T also allowed us to examine the eye-selectivity responses across the cortical depth, which are expected to be strongest in the middle layers. We observed a substantial increase in the percentage of eye-selective voxels, as well as a doubling in run-to-run consistency of eye preference at ultrahigh field compared to 3 Tesla. We also found that across cortical depth, eye selectivity increased towards the superficial layers, and that signal contrast increased while noise remained nearly constant towards the surface. The depth-resolved results are consistent with a distortion of spatial specificity of the GE-EPI signal by ascending venules and large draining veins on the cortical surface. The effects of larger vessels cause increasing signal amplitude, but also displacement of the maximum BOLD signal relative to neural activity. In summary, our results show that increase in spatial resolution, reduced partial volume effects, and improved sensitivity at 9.4 T allow for better detection of eye-selective signals related to ocular dominance columns. However, although ultrahigh field yields higher sensitivity to the ocular dominance signal, GE-EPI still suffers from specificity issues, with a prominent signal contribution at shallow depths from larger cortical vessels.

中文翻译：

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人类初级视觉皮层的眼睛选择性 fMRI 活动：3 T 和 9.4 T 之间的比较，以及皮层深度的影响

人类的初级视觉皮层包含优先响应刺激一只眼睛（眼球优势柱）的神经元斑块。大多数先前报告 V1 中眼睛特定活动的 fMRI 研究使用 4 T 或更高的磁场强度。然而，也有报道称在 3 T 下也有可靠的眼睛选择性激活。在这项研究中，我们研究了使用高分辨率 GE-EPI fMRI 在 3 Tesla 和亚毫米分辨率 fMRI 在超高 9.4 Tesla 磁场强度下检测眼睛选择性 V1 活动的可能性，采集参数针对每个场强度进行了优化。9.4 T 的高分辨率 fMRI 还允许我们检查整个皮层深度的眼睛选择性反应，预计这些反应在中间层最强。我们观察到眼睛选择性体素的百分比显着增加，并且与 3 特斯拉相比，超高场下眼睛偏好的逐次运行一致性增加了一倍。我们还发现，在整个皮层深度，眼睛对表层的选择性增加，信号对比度增加，而表面的噪声几乎保持不变。深度解析的结果与皮质表面上小静脉和大引流静脉对 GE-EPI 信号空间特异性的扭曲一致。较大血管的影响会导致信号幅度增加，但也会导致最大 BOLD 信号相对于神经活动的位移。总而言之，我们的结果表明空间分辨率增加，部分体积效应减少，灵敏度提高 9。4 T 允许更好地检测与眼优势列相关的眼选择性信号。然而，尽管超高场对眼优势信号产生更高的敏感性，但 GE-EPI 仍然存在特异性问题，在较大皮层血管的浅深度处具有显着的信号贡献。