Marquis Renaud, Muller Sandrine, Lorio Sara, Rodriguez-Herreros Borja, Melie-Garcia Lester, Kherif Ferath, Lutti Antoine, Draganski Bogdan
Laboratory for Research in Neuroimaging, LREN, Department of Clinical Neurosciences, Lausanne University Hospital, CHUV, University of Lausanne, Lausanne, Switzerland.
EEG and Epilepsy Unit, Department of Clinical Neuroscience, Faculty of Medicine, Geneva University Hospitals, Geneva, Switzerland.
Front Neurosci. 2019 Jun 11;13:571. doi: 10.3389/fnins.2019.00571. eCollection 2019.
There is much controversy about the optimal trade-off between blood-oxygen-level-dependent (BOLD) sensitivity and spatial precision in experiments on brain's topology properties using functional magnetic resonance imaging (fMRI). The sparse empirical evidence and regional specificity of these interactions pose a practical burden for the choice of imaging protocol parameters. Here, we test in a motor somatotopy experiment the impact of fMRI spatial resolution on differentiation between body part representations in cortex and subcortical structures. Motor somatotopy patterns were obtained in a block-design paradigm and visually cued movements of face, upper and lower limbs at 1.5, 2, and 3 mm spatial resolution. The degree of segregation of the body parts' spatial representations was estimated using a pattern component model. In cortical areas, we observed the same level of segregation between somatotopy maps across all three resolutions. In subcortical areas the degree of effective similarity between spatial representations was significantly impacted by the image resolution. The 1.5 mm 3D EPI and 3 mm 2D EPI protocols led to higher segregation between motor representations compared to the 2 mm 3D EPI protocol. This finding could not be attributed to differential BOLD sensitivity or delineation of functional areas alone and suggests a crucial role of the image encoding scheme - i.e., 2D vs. 3D EPI. Our study contributes to the field by providing empirical evidence about the impact of acquisition protocols for the delineation of somatotopic areas in cortical and sub-cortical brain regions.
在使用功能磁共振成像（fMRI）对大脑拓扑特性进行实验时，关于血氧水平依赖（BOLD）敏感性与空间精度之间的最佳权衡存在诸多争议。这些相互作用的稀疏实证证据和区域特异性给成像协议参数的选择带来了实际负担。在此，我们在一项运动躯体感觉定位实验中测试了fMRI空间分辨率对皮质和皮质下结构中身体部位表征差异的影响。在一个组块设计范式中获得运动躯体感觉定位模式，并在1.5毫米、2毫米和3毫米空间分辨率下对脸部、上肢和下肢的视觉提示运动进行测试。使用模式成分模型估计身体部位空间表征的分离程度。在皮质区域，我们观察到在所有三种分辨率下躯体感觉定位图之间的分离水平相同。在皮质下区域，空间表征之间的有效相似程度受到图像分辨率的显著影响。与2毫米3D EPI协议相比，1.5毫米3D EPI和3毫米2D EPI协议导致运动表征之间的分离度更高。这一发现不能仅归因于不同的BOLD敏感性或功能区域的描绘，表明图像编码方案（即2D与3D EPI）起着关键作用。我们的研究通过提供关于采集协议对皮质和皮质下脑区躯体感觉区域描绘影响的实证证据，为该领域做出了贡献。
