Capgras Delusion

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The Capgras Delusion is one of the rarest and colorful syndromes in neurology. The patient fails to recognise the faces of close acquaintances and calls them as an ‘imposter’. They claim that the person ‘looks like’ or is ‘identical to’ someone they know, while continuing to believe that they are two different individuals. The delusional belief is strongest when the putative imposter is present [2]. Capgras delusion is classified as a delusional misidentification syndrome, a class of beliefs where the patients have delusional beliefs that involves misidentification of people, places or objects.
The delusion is mostly common in patients diagnosed with neurodegenerative diseases; such as Alzheimer’s disease (2% - 30%) [8],
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Adapted from Ellis et al. (1997), Proc. R. Soc. B.

This theory fails to answer two major questions. First, why is the phenomenon specific to close relatives? One possibility, as suggested by Ramachandran el al., is that only with parents or a spouse does one seek emotional arousal thus its absence leads to a confabulatory delusion that one’s parent is an imposter. With an emotionally neutral person on the other hand, one does not expect such arousal, and therefore there is no incentive for generating a delusion. The second major question is why the lack of emotional arousal can have such drastic delusions? Why does the patient not accept the fact that the loved one is not an imposter but can no longer feel the warmth? There can be some extra lesions, perhaps in the right frontal cortex, which is responsible for generating such an extreme delusion. The left hemisphere seeks to preserve consistency by explaining for any discrepancies, whereas there may be a global ‘consistency checking’ mechanism in the right hemisphere which serves to counter-balance this tendency (Ramachandran 1995).
Damage to such a mechanism due to a right hemisphere stroke may lead to Capgras Delusion, where one needs a conjugation of two lesions: one which affects the global consistency-checking mechanism in the right hemisphere and the other affecting the consistency.
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