Provocation of Symmetry/Ordering Symptoms in Anorexia nervosa: A Functional Neuroimaging Study

Anorexia nervosa (AN), obsessive–compulsive disorder (OCD), and obsessive–compulsive personality disorder (OCPD) are often co-morbid; however, the aetiology of such co-morbidity has not been well investigated. This study examined brain activation in women with AN and in healthy control (HC) women during the provocation of symmetry/ordering-related anxiety. During provocation, patients with AN showed more anxiety compared to HCs, which was correlated with the severity of symmetry/ordering symptoms. Activation in the right parietal lobe and right prefrontal cortex (rPFC) in response to provocation was reduced in the AN group compared with the HC group. The reduced right parietal activation observed in the AN group is consistent with parietal lobe involvement in visuospatial cognition and with studies of OCD reporting an association between structural abnormalities in this region and the severity of ‘ordering’ symptoms. Reduced rPFC activation in response to symmetry/ordering provocation has similarities with some, but not all, data collected from patients with AN who were exposed to images of food and bodies. Furthermore, the combination of data from the AN and HC groups showed that rPFC activation during symptom provocation was inversely correlated with the severity of symmetry/ordering symptoms. These data suggest that individuals with AN have a diminished ability to cognitively deal with illness-associated symptoms of provocation. Furthermore, our data also suggest that symptom provocation can progressively overload attempts by the rPFC to exert cognitive control. These findings are discussed in the context of the current neurobiological models of AN.神经性厌食症（Anorexia nervosa, AN）、强迫症（Obsessive–compulsive disorder, OCD）与强迫型人格障碍（Obsessive–compulsive personality disorder, OCPD）常存在共病现象，但此类共病的病因学机制尚未得到充分研究。本研究针对女性神经性厌食症患者与健康对照（Healthy Control, HC）女性，考察了对称/排序相关焦虑诱发过程中的脑激活特征。在焦虑诱发过程中，神经性厌食症患者的焦虑水平显著高于健康对照，且该水平与对称/排序症状的严重程度呈正相关。相较于健康对照组，神经性厌食症组在面对诱发刺激时，右侧顶叶与右侧前额叶皮层（Right Prefrontal Cortex, rPFC）的激活程度显著降低。神经性厌食症组观察到的右侧顶叶激活减弱，与顶叶参与视空间认知的功能特点相符，也与此前强迫症相关研究的结果一致——该脑区的结构异常与“排序”症状的严重程度存在关联。对称/排序焦虑诱发过程中右侧前额叶皮层激活减弱的现象，与部分针对暴露于食物与身体图像的神经性厌食症患者的研究结果相似，但并非全部吻合。进一步整合两组受试者的数据后发现，症状诱发过程中的右侧前额叶皮层激活程度与对称/排序症状的严重程度呈负相关。上述结果提示，神经性厌食症患者在认知应对与疾病相关的诱发症状时存在能力受损。此外，本研究数据还表明，症状诱发过程可逐步加重右侧前额叶皮层执行认知控制的负荷。本研究结果将结合当前神经性厌食症的神经生物学模型展开讨论。