Functional organization of human occipital-callosal fiber tracts
Functional organization of human occipital-callosal fiber tracts
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DOI：
10.1073/pnas.0500003102
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发表时间：
2005-05-17
影响因子：
11.1
通讯作者：
Wandell, BA
中科院分区：
文献类型：
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作者：
Dougherty, RF;Ben-Shachar, M;Wandell, BA
扩散张量成像（DTI）和纤维追踪（FT）被用于测量个体人类受试者中连接两个半球的枕叶纤维束。这些纤维束对正常视觉很重要。而且，这些纤维束部分受损与失读症有关。为了评估DTI - FT测量的可靠性，分别从每个受试者的左右半球独立估计枕叶 - 胼胝体投射。左右估计在胼胝体压部内收敛到相同位置。我们通过将其与功能性磁共振成像相结合，进一步描述了估计的枕叶 - 胼胝体纤维束的特性。我们利用功能性磁共振成像来识别皮质中的视野图，并根据纤维端点处的皮质功能反应标记纤维。这种标记揭示了胼胝体压部内纤维的规则组织。背侧视野图（背侧V3、V3A、V3B、V7）通过胼胝体压部中间的一个大带发送投射，而腹侧视野图（腹侧V3、V4）通过胼胝体压部的下前角发送投射。独立的左右估计之间的一致性，再加上先前对猕猴同源纤维束的描述，验证了DTI - FT方法。然而，这些方法的一个主要局限性是灵敏度低：大量连接腹侧和外侧视觉皮质同位区域的纤维束未被检测到。我们得出结论，大多数估计的纤维束是真实的，并且可以精确到1 - 2毫米定位，但由于数据和算法的局限性，许多纤维束被遗漏。
Diffusion tensor imaging (DTI) and fiber tracking (FT) were used to measure the occipital lobe fiber tracts connecting the two hemispheres in individual human subjects. These tracts are important for normal vision. Also, damage to portions of these tracts is associated with alexia. To assess the reliability of the DTI-FT measurements, occipital-callosal projections were estimated from each subject's left and right hemispheres independently, The left and right estimates converged onto the same positions within the splenium. We further characterized the properties of the estimated occipital-callosal fiber tracts by combining them with functional MRI. We used functional MRI to identify visual field maps in cortex and labeled fibers by the cortical functional response at the fiber endpoint. This labeling reveals a regular organization of the fibers within the splenium. The dorsal visual maps (dorsal V3, V3A, V3B, V7) send projections through a large band in the middle of the splenium, whereas ventral visual maps (ventral V3, V4) send projections through the inferior-anterior corner of the splenium. The agreement between the independent left/right estimates, further supported by previous descriptions of homologous tracts in macaque, validates the DTI-FT methods. However, a principal limitation of these methods is low sensitivity: a large number of fiber tracts that connect homotopic regions of ventral and lateral visual cortex were undetected. We conclude that most of the estimated tracts are real and can be localized with a precision of 1-2 mm, but many tracts are missed because of data and algorithm limitations.