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 . 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 ...view middle of the document...
The paper suggested that there are two components of the visual recognition of a familiar face. One is associated with conscious recognition of the face and recall of associated semantic information, whereas the other is responsible for the limbic mediated emotional arousal. An emotional arousal is related with the emotional valence, including a sense of familiarity which accompanies the conscious recognition of a familiar face . However, the patients are often mentally lucid in all other aspects. They do not suffer from a global breakdown in rationality.
An explanation by Bauer et al,. suggested that the syndrome represents a ‘mirror image’ of prosopagnosia in which the ventral route from the visual centers to the temporal lobes may be preserved allowing conscious face recognition but the dorsal visual route responsible for giving the face its emotional significance is damaged. The only way patients make sense of the absence of this emotional arousal is to form the belief that the person he is looking at is an imposter .
Bauer (1984), using a technique normally employed in forensic lie detection, noted that the prosopagnosic patient revealed elevated skin-conductance responses (SCR) to previously
familiar faces even though he could not consciously identify them. Normal individuals show reduced SCR to familiar compared with unfamiliar faces [13,14]. People with Capgras Syndrome lack the usual input regarding a face’s personal significance. As such, the absence of this information regarding the face of someone particularly close can be the precursor to the delusion.
Ellis et al., found that five patients with Capgras Syndrome, when shown a series of familiar and unfamiliar faces, did not demonstrate the same SCR differences as either matched psychiatric patients or normal controls. (see Fig. 1)
Fig.1: Skin conductance response to familiar and unfamiliar faces by five individuals with the Capgras Delusion and matched psychiatric and normal controls. 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...