Spatial smoothing of functional magnetic resonance imaging (fMRI) data can be performed on volumetric images and on the extracted surface of the brain. Smoothing on the unfolded cortex should theoretically improve the ability to separate signals between brain areas that are near together in the folded cortex but are more distant in the unfolded cortex. However, surface-based method approaches (SBA) are currently not utilized as standard procedure in the preprocessing of neuroimaging data. Recent improvements in the quality of cortical surface modeling and improvements in its usability nevertheless advocate this method. In the current study, we evaluated the benefits of an up-to-date surface-based smoothing in comparison to volume-based smoothing. We focused on the effect of signal contamination between different functional systems using the primary motor and primary somatosensory cortex as an example. We were particularly interested in how this signal contamination influences the results of activity and connectivity analyses for these brain regions. We addressed this question by performing fMRI on 19 subjects during a tactile stimulation paradigm and by using simulated BOLD responses. We demonstrated that volume-based smoothing causes contamination of the primary motor cortex by somatosensory cortical responses, leading to false positive motor activation. These false positive motor activations were not found by using surface-based smoothing for reasonable kernel sizes. Accordingly, volume-based smoothing caused an exaggeration of connectivity estimates between these regions. In conclusion, this study showed that surface-based smoothing decreases signal contamination considerably between neighboring functional brain regions and improves the validity of activity and connectivity results.

功能磁共振成像（fMRI）数据的空间平滑可以在体积图像和提取的大脑表面上执行。理论上，对展开的皮质进行平滑处理应该可以改善在折叠的皮质中靠近在一起但在展开的皮质中距离较远的大脑区域之间分离信号的能力。但是，基于表面的方法（SBA）目前尚未在神经影像数据的预处理中用作标准程序。尽管如此，皮质表面建模质量的最新改进及其可用性的改进仍提倡该方法。在当前的研究中，我们评估了与基于体积的平滑相比，最新的基于表面的平滑的好处。我们以主要电机和主要体感皮层为例，重点研究了不同功能系统之间信号污染的影响。我们对这种信号污染如何影响这些大脑区域的活动和连接性分析的结果特别感兴趣。我们通过在触觉刺激范例中对19位受试者执行fMRI并使用模拟的BOLD响应来解决此问题。我们证明了基于体的平滑会导致体感皮层反应污染初级运动皮层，从而导致假阳性运动激活。通过使用基于表面的平滑处理获得合理的内核大小，未发现这些错误的正向电机激活。因此，基于体积的平滑导致这些区域之间的连通性估计过大。结论，