Department of Psychiatry, Seoul National University College of Medicine, Seoul, Korea.
Hum Brain Mapp. 2012 Oct;33(10):2441-52. doi: 10.1002/hbm.21372. Epub 2011 Sep 16.
It is widely accepted that abnormalities in the frontal area of the brain underpin the pathophysiology of obsessive-compulsive disorder (OCD). Fundamental to this investigation is the delineation of frontal white matter tracts including dorsal and ventral frontal projections of interhemispheric connections. While previous investigations of OCD have examined the dorsal and ventral frontal regions, the corresponding callosal connections have not been investigated, despite their importance. We recruited twenty patients with OCD (15 drug-naïve and 5 currently unmedicated) and demographically similar healthy controls, and conducted fiber tractography and post hoc quantitative analysis using diffusion tensor imaging. We extracted fractional anisotropy (FA) of the fronto-callosal fibers along the entire length of the tract. Function-specific [by the Brodmann area region-of-interest (ROI) approach] and region-specific (by the length-parameterization approach) tracts were defined. In addition, we devised a new index of dorsal-ventral imbalance (DVII) of fiber integrity. Significant FA decreases were observed in orbitofrontal and dorsolateral prefrontal projections of the corpus callosum (P < 0.05, false discovery rate-corrected) with higher function/region sensitivity than voxel-based or ROI-based approaches. Importantly, OCD patients also exhibited significantly higher ventral-greater-than-dorsal asymmetry of FA values than normal controls (P < 0.05, FDR-corrected). This study is the first to investigate fiber integrity in the dorsal/ventral frontal parts of the callosal tractography in unmedicated OCD patients. Using a more quantitative method in terms of functional and regional specificity than previous studies, we report abnormalities in interhemispheric connectivity of both dorsal and ventral networks in the pathophysiology of OCD.
人们普遍认为，大脑额叶区域的异常是强迫症（OCD）病理生理学的基础。这项研究的基础是描绘额叶白质束，包括大脑两半球间连接的背侧和腹侧额叶投射。虽然以前对 OCD 的研究检查了背侧和腹侧额叶区域，但对应的胼胝体连接尚未得到研究，尽管它们很重要。我们招募了 20 名强迫症患者（15 名未用药和 5 名未用药）和年龄、性别相匹配的健康对照者，并进行了纤维束追踪和弥散张量成像的事后定量分析。我们提取了整个纤维束的额胼胝体纤维的分数各向异性（FA）。采用功能特异性（通过 Brodmann 区 ROI 方法）和区域特异性（通过长度参数化方法）的方法定义了纤维束。此外，我们设计了一个新的纤维完整性背侧-腹侧不平衡（DVII）指数。在胼胝体的眶额和背外侧前额叶投射中观察到 FA 值显著降低（P < 0.05，经假发现率校正），其功能/区域敏感性高于体素或 ROI 方法。重要的是，与正常对照组相比，强迫症患者的 FA 值的腹侧-大于-背侧不对称性也显著升高（P < 0.05，经 FDR 校正）。这项研究是首次在未用药的 OCD 患者中研究胼胝体纤维束追踪术的背侧/腹侧额叶部分的纤维完整性。与以前的研究相比，我们使用了更具功能和区域特异性的更定量的方法，报告了 OCD 病理生理学中背侧和腹侧网络之间的半球间连接异常。
