Wong Wan-Wa, Peel Hayden, Cabeen Ryan, Diaz-Fong Joel P, Feusner Jamie D
Centre for Addiction and Mental Health, Toronto, ON, Canada.
Hong Kong Center for Neurodegenerative Diseases, Hong Kong Science Park, Hong Kong, China.
bioRxiv. 2024 Jul 16:2024.07.12.603273. doi: 10.1101/2024.07.12.603273.
Individuals with body dysmorphic disorder (BDD) perceive distortions in their appearance, which could be due to imbalances in global and local visual processing. The vertical occipital fasciculus connects dorsal and ventral visual stream regions, integrating global and local information, yet the role of this structural connection in BDD has not been explored. Here, we investigated the vertical occipital fasciculus's white matter microstructure in those with BDD and healthy controls and tested associations with psychometric measures and effective connectivity while viewing their face during fMRI.
We analyzed diffusion MRI and fMRI data in 17 unmedicated adults with BDD and 21 healthy controls. For diffusion MRI, bundle-specific analysis was performed, enabling quantitative estimation of neurite density and orientation dispersion of the vertical occipital fasciculus. For task fMRI, participants naturalistically viewed photos of their own face, from which we computed effective connectivity from dorsal to ventral visual regions.
In BDD, neurite density was negatively correlated with appearance dissatisfaction and negatively correlated with effective connectivity. Further, those with weaker effective connectivity while viewing their face had worse BDD symptoms and worse insight. In controls, no significant relationships were found between any of the measures. There were no significant group differences in neurite density or orientation dispersion.
Those with BDD with worse appearance dissatisfaction have a lower fraction of tissue having axons or dendrites along the vertical occipital fasciculus bundle, possibly reflecting impacting the degree of integration of global and local visual information between the dorsal and ventral visual streams. These results provide early insights into how the vertical occipital fasciculus's microstructure relates to the subjective experience of one's appearance, as well as the possibility of distinct functional-structural relationships in BDD.
患有躯体变形障碍（BDD）的个体感知到自己外貌存在扭曲，这可能是由于整体和局部视觉处理失衡所致。枕颞垂直束连接背侧和腹侧视觉流区域，整合整体和局部信息，但这种结构连接在BDD中的作用尚未得到探索。在此，我们研究了BDD患者和健康对照者的枕颞垂直束白质微观结构，并在功能磁共振成像（fMRI）期间观察他们的面部时，测试了其与心理测量指标及有效连接性的关联。
我们分析了17名未接受药物治疗的BDD成年患者和21名健康对照者的扩散磁共振成像（MRI）和fMRI数据。对于扩散MRI，进行了束特异性分析，能够定量估计枕颞垂直束的神经突密度和方向离散度。对于任务fMRI，参与者自然地观看自己面部的照片，我们据此计算从背侧到腹侧视觉区域的有效连接性。
在BDD患者中，神经突密度与外貌不满呈负相关，与有效连接性也呈负相关。此外，那些在观看自己面部时有效连接性较弱的患者，其BDD症状更严重，自知力更差。在对照组中，未发现任何测量指标之间存在显著关系。神经突密度或方向离散度在两组之间无显著差异。
外貌不满更严重的BDD患者，其枕颞垂直束束中具有轴突或树突的组织比例较低，这可能反映出影响了背侧和腹侧视觉流之间整体和局部视觉信息的整合程度。这些结果为枕颞垂直束的微观结构如何与个体外貌的主观体验相关，以及BDD中独特的功能 - 结构关系的可能性提供了早期见解。
