|The man was diagnosed with |
Mr B, who had no history of psychiatric illness, was diagnosed with a form of Capgras syndrome. People with Capgras believe that one or more familiar people have been replaced by identical strangers, and it falls within the delusional misidentification syndrome, together with related conditions such as the Fregoli delusion: the belief that many people you encounter are actually a single deceiver in disguise. It’s likely that such delusions involve some degree of impairment in face processing, specifically the ability to process familiarity of other people’s faces: in Cagras the familiar feel somehow not (an experience undergirded by skin conductance response data); in Fregoli the many feel somehow the same. If this hypothesis bears out, these delusions could be seen as the complement – or mirror image – of prosopagnosia (also known as face-blindness), where explicit recognition of faces is impaired, but sufferers still retain their implicit feelings about faces, correctly guessing which belong to people they know.
What’s interesting about Mr B’s mirrored-Capgras, also called mirrored self-misidentification, is that the delusional judgment is applied to one’s own face. Evidence suggests that our brains process own-face information in a special way, suggesting that this particular experience reflects a specific brain impairment, rather than the delusion arbitrarily settling on one target rather than another. The authors of the Neurocase article don’t report too deeply on Mr B’s neurological symptoms, mentioning only some protein indicators consistent with Alzheimer’s Disease, and atrophy in chiefly posterior brain regions. We would expect some damage also within the dorsolateral prefrontal cortex, as this is typical in patients experiencing such delusions. This area is involved in evaluating beliefs, stepping in to question extreme or incoherent ideas.
Mr B was given antidepressant and antipsychotic medication in hospital, and three months later, he had recovered from his delusion: “Mr. B. explained that his double had gone.” It’s nearly Halloween, where we get to play tricks with the uncanny. Maybe spare a thought for the tricks that that the uncanny can play on us.
Diard-Detoeuf, C., Desmidt, T., Mondon, K., & Graux, J. (2015). A case of Capgras syndrome with one’s own reflected image in a mirror Neurocase, 1-2 DOI: 10.1080/13554794.2015.1080847
Note: photograph is a stock image and does not portray Mr B.
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Post written by Alex Fradera (@alexfradera) for the BPS Research Digest.
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