Here we describe a rare case of Capgras delusion – a misidentification syndrome characterized by the belief that a person has been replaced by an imposter – in a patient without evident neurological or psychiatric symptoms. Intriguingly, delusional belief was selective for both person and modality, as the patient believed that his son – not his daughter or other relatives – was substituted with an imposter only while being in presence of him and looking at his face, but not when merely listening to his voice.

A neuroanatomical reconstruction obtained integrating morphological and functional patient’s neuroimaging data highlighted two main peculiarities: a compression of the rostral portion of right temporal lobe due to a large arachnoid cyst, and a bilaterally reduced metabolism of frontal areas. Autonomic data obtained from thermal infra-red camera and skin conductance recordings showed that a higher sympathetic activation was evoked by the observation of daughter’s face, relative to the observation of the son’s face as well as of not-familiar faces; conversely, daughter and son voices elicited a similar sympathetic activation, higher relative to not-familiar voices, indicating a modality-dependent dissociation consistent with the delusional behavior.

Our case supports the “two-hit hypothesis” about Capgras delusion etiopathogenesis: here, the first hit is represented by the right-temporal lesion impairing the association between familiar faces and emotional values, the second one is the frontal bilateral hypometabolism favoring delusional behavior. The selective occurrence of “imposter” delusion for a particular subject and for a specific perceptual modality suggests the involvement of modality-specific interactions in the retrieval of affective properties during familiar people recognition.

在这里，我们描述了一种罕见的卡普格拉斯妄想病例，这是一种误诊症候群，其特征是认为患者已经被冒名顶替者取代了，而该患者没有明显的神经或精神症状。有趣的是，妄想信仰对人格和情态都具有选择性，因为患者认为只有当他的儿子（而不是他的女儿或其他亲戚）在他面前并看着他的脸时，才用冒名顶替者代替，而仅在听他讲话时却不会他的声音。

结合形态和功能患者的神经影像学数据获得的神经解剖学重建突出了两个主要特点：由于大的蛛网膜囊肿而压缩了右颞叶的鼻端部分，并且额叶的新陈代谢双侧减少。从红外热像仪和皮肤电导记录中获得的自主数据表明，与观察儿子的脸以及不熟悉的脸相比，观察女儿的脸会引起更高的交感神经激活。相反，女儿和儿子的声音引起类似的共鸣激活，相对于不熟悉的声音更高，表明与妄想行为一致的依赖于情态的分离。

我们的案例支持关于卡普格拉斯妄想病因的“两次打击假说”：在这里，第一次打击以右颞部病变为代表，损害了熟悉的面孔和情感价值之间的联系，第二次打击是额叶双侧代谢不足，有利于妄想行为。针对特定对象和特定感知模态的“冒名顶替者”妄想的选择性发生表明，在熟悉的人识别过程中，特定于模态的交互参与了情感属性的检索。