Abstract
Patients with Capgras syndrome (CS) adopt the delusional belief that persons well-known to them have been replaced by an imposter. Several current theoretical models of CS attribute such misidentification problems to deficits in covert recognition processes related to the generation of appropriate affective autonomic signals. These models assume intact overt recognition processes for the imposter and, more broadly, for other individuals. As such, it has been suggested that CS could reflect the “mirror-image” of prosopagnosia. The purpose of the current study was to determine whether overt person recognition abilities are indeed always spared in CS. Furthermore, we examined whether CS might be associated with any impairments in overt affective judgments of facial expressions. We pursued these goals by studying a patient with Dementia with Lewy bodies (DLB) who showed clear signs of CS, and by comparing him to another patient with DLB who did not experience CS, as well as to a group of healthy control participants. Clinical magnetic resonance imaging scans revealed medial prefrontal cortex (mPFC) atrophy that appeared to be uniquely associated with the presence CS. We assessed overt person recognition with three fame recognition tasks, using faces, voices, and names as cues. We also included measures of confidence and probed pertinent semantic knowledge. In addition, participants rated the intensity of fearful facial expressions. We found that CS was associated with overt person recognition deficits when probed with faces and voices, but not with names. Critically, these deficits were not present in the DLB patient without CS. In addition, CS was associated with impairments in overt judgments of affect intensity. Taken together, our findings cast doubt on the traditional view that CS is the mirror-image of prosopagnosia and that it spares overt recognition abilities. These findings can still be accommodated by models of CS that emphasize deficits in autonomic responding, to the extent that the potential role of interoceptive awareness in overt judgments is taken into account.
Highlights
Misidentification syndromes are among the most fascinating and puzzling forms of memory problems that can result from psychiatric or neurological disease
Perhaps the most striking condition is Capgras syndrome (CS), in which individuals come to adopt the delusional belief that persons well-known to them have been replaced by an impostor or a “double.” A defining characteristic of delusions that is present in CS is that patients will firmly hold on to their delusional beliefs in the presence of mounting contradictory evidence
GENERAL DISCUSSION The current case study aimed to examine the scope of overt person recognition impairments associated with CS in Dementia with Lewy bodies (DLB), focusing on both the recognition of identity and affect as conveyed through facial expressions
Summary
Misidentification syndromes are among the most fascinating and puzzling forms of memory problems that can result from psychiatric or neurological disease. They are monothematic delusions that have intrigued psychologists and philosophers alike for over a century, but have only recently been brought into the realm of scientific investigation. Perhaps the most striking condition is Capgras syndrome (CS), in which individuals come to adopt the delusional belief that persons well-known to them have been replaced by an impostor or a “double.” A defining characteristic of delusions that is present in CS is that patients will firmly hold on to their delusional beliefs in the presence of mounting contradictory evidence. While commonly observed in the context of psychiatric disease, CS can result from various neurological conditions. The purpose of the current study is to shed more light on the nature of cognitive and affective deficits associated with CS in the context of neurodegenerative disease
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