Capgras syndrome is down one of the stranger avenues of neurological conditions. It’s characterized by delusional beliefs that a person – often a family member, loved one, spouse or friend – has been replaced by an imposter doppelgänger.
As if that couldn't get more peculiar, Harvard neurologists have recently published a paper in the journal Neurocase about a man suffering from what they have coined “Cat-gras Delusions.” In the paper, they detail the first known case of a person whose Capgras delusions were centered on their pet cat.
Among his medical records, they found that the 71-year-old man had a history of heavy drinking, sports-related head injuries, and bipolar disorder. Six years previous to the unusual thoughts occurring, he had stopped taking his psychiatric medications and consequently began suffering from delusions that the FBI was monitoring him. His thoughts then moved to his cat, believing it had been replaced by an identical masquerader who was also involved in the conspiracy against him.
The study explained that “he knew that the current cat resembled his pet cat physically, but that the personality or psychic core of his cat had been replaced.”
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The neurologists explained that these delusional beliefs are caused by a glitch when retrieving autobiographical memory, a collection of our past experiences. Normally, when we perceive an external stimulus, our brain has to retrieve information from our internal catalog of autobiographical memories. This process allows us to associate new stimuli with past experiences. However, in the case of Capgras delusions, the patient’s perception of an external object doesn’t trigger the appropriate retrieval of autobiographical memory.
This can lead to them associating the external stimulus with the “practical” attributes, such as its appearance, but not an association with their emotional memory, leading to this lack of familiarity with a physically recognizable object.
From information gathered through brain scans, the neurologists believe the erroneous thought pattern was linked to deterioration of his cerebral cortex, the region concerned with higher cognitive skills, in a process similar to dementia. This was no doubt aggravated by the numerous head traumas he received while playing ice hockey.
Much like this case, Capgras syndrome is strongly linked to other neurological diseases and mental health issues. It’s believed that 81 percent of Capgras sufferers have some form of neurodegenerative disease, most commonly Lewy body disease.
Why exactly this man’s delusions were centered on his cat – and not, say, his wife – remains a mystery. However, while this is the first case of “Cat-gras Delusions,” there have been two reported cases of Capgras delusions towards a pet dog and two cases towards pet birds.
Main image credit: Gwydion M. Williams/Flickr. (CC BY 2.0)