PDF(Pubmed)
Abstract：
White matter (WM) functional activity has been reliably detected through functional magnetic resonance imaging (fMRI). Previous studies have primarily examined WM bundles as unified entities, thereby obscuring the functional heterogeneity inherent within these bundles. Here, for the first time, we investigate the function of sub-bundles of a prototypical visual WM tract-the optic radiation (OR). We use the 7T retinotopy dataset from the Human Connectome Project (HCP) to reconstruct OR and further subdivide the OR into sub-bundles based on the fiber\'s termination in the primary visual cortex (V1). The population receptive field (pRF) model is then applied to evaluate the retinotopic properties of these sub-bundles, and the consistency of the pRF properties of sub-bundles with those of V1 subfields is evaluated. Furthermore, we utilize the HCP working memory dataset to evaluate the activations of the foveal and peripheral OR sub-bundles, along with LGN and V1 subfields, during 0-back and 2-back tasks. We then evaluate differences in 2bk-0bk contrast between foveal and peripheral sub-bundles (or subfields), and further examine potential relationships between 2bk-0bk contrast and 2-back task d-prime. The results show that the pRF properties of OR sub-bundles exhibit standard retinotopic properties and are typically similar to the properties of V1 subfields. Notably, activations during the 2-back task consistently surpass those under the 0-back task across foveal and peripheral OR sub-bundles, as well as LGN and V1 subfields. The foveal V1 displays significantly higher 2bk-0bk contrast than peripheral V1. The 2-back task d-prime shows strong correlations with 2bk-0bk contrast for foveal and peripheral OR fibers. These findings demonstrate that the blood oxygen level-dependent (BOLD) signals of OR sub-bundles encode high-fidelity visual information, underscoring the feasibility of assessing WM functional activity at the sub-bundle level. Additionally, the study highlights the role of OR in the top-down processes of visual working memory beyond the bottom-up processes for visual information transmission. Conclusively, this study innovatively proposes a novel paradigm for analyzing WM fiber tracts at the individual sub-bundle level and expands understanding of OR function.
摘要：
已通过功能磁共振成像（fMRI）可靠地检测了白质（WM）功能活动。以前的研究主要将WM捆绑包作为统一的实体进行检查，从而掩盖了这些束中固有的功能异质性。这里,第一次,我们研究了典型视觉WM束的子束-光学辐射（OR）的功能。我们使用来自HumanConnectome项目（HCP）的7T视网膜变性数据集来重建OR，并根据纤维在初级视觉皮层（V1）中的终止将OR进一步细分为子束。然后应用群体感受野（pRF）模型来评估这些子束的视网膜定位特性，并评估了子束的pRF属性与V1子场的pRF属性的一致性。此外，我们利用HCP工作记忆数据集来评估中央凹和周边OR子束的激活，以及LGN和V1子字段，在0-back和2-back任务期间。然后，我们评估中央凹和外围子束（或子场）之间的2bk-0bk对比度的差异，并进一步检查2bk-0bk对比度和2回任务d-prime之间的潜在关系。结果表明，OR子束的pRF特性表现出标准的视网膜定位特性，并且通常类似于V1子场的特性。值得注意的是,在中央凹和外围OR子束中，2-back任务期间的激活始终超过0-back任务下的激活，以及LGN和V1子字段。中央凹V1的2bk-0bk对比度明显高于周边V1。2-back任务d-prime显示出与中央凹和周围OR纤维的2bk-0bk对比度的强相关性。这些发现表明，OR子束的血氧水平依赖性（BOLD）信号编码高保真的视觉信息，强调在子束水平上评估WM功能活动的可行性。此外,该研究强调了OR在视觉工作记忆的自上而下过程中的作用，而不是视觉信息传递的自下而上过程。最后，这项研究创新性地提出了一种在单个子束水平上分析WM纤维束的新范式，并扩展了对OR函数的理解。
