Capgras delusizon (CD) Essay
Capgras delusion (CD) is a is a rare condition in which patients believe that people close to them, usually parents, spouses, and children, have been replaced by identically looking impostors. It was named after French Professor Jean-Marie Joseph Capgras who first reported it in 1923 with his intern Jean Reboul-Lachaux. Although Capgras delusion patients are capable of recognizing familiar faces, they present a delusional belief that some relatives have been replaced by impostors. Capgras delusizon (CD) Essay.Understanding the neurological defects in Capgras delusion opens a window to understanding the mechanisms underlying the identification and recognition of individuals by the human brain. This paper will demonstrate that this process is modulated by a single neurological pathway as well as two distinct cognitive routes, a covert and an over one, through an analysis of proposed models of facial recognition coupled with examination of some Capgras delusion case studies.
It has been first posited that Capgras delusion is a psychological disorder as it occurs predominantly in patients suffering from schizophrenia or other types of psychosis. As such, the early models proposed to explain it were psychodynamic theories inspired by psychoanalysis. Capgras himself believed that the delusion resulted from, not a sensory but an affective disorder that puts in conflict a sense of familiarity and a sense of strangeness elicited by the visual stimulus which he compared to the mixed feelings one has when confronted with someone one hasn’t seen in a long time. Another theory, depersonalization, hypothesizes that patients find it easier to believe that others changed rather then themselves and so they project their impression of not being themselves to the impression that others are not being themselves. The most widely accepted theory currently is the hypothesis that Capgras delusion is a psychotic solution to the problem of ambivalence which stipulates that the defense mechanism used to cope with the simultaneous feelings of love and hate that patients feel towards their relatives would be the existence of a sosie, perceived as the imposter, for which the patient can feel hatred without experiencing guilt for resenting them. Capgras delusizon (CD) Essay.
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With hindsight, it came to light that 33% of the documented cases of CD resulted from traumatic brain lesions which suggests an organic basis to the condition (Signer 1994) and thus lead to the classification of Capgras delusion as a functional neuropsychological deficit. This resulted in the development of neuro-lesional models, starting from the 1960s, with the objective of locating the face processing area in the human brain, using anatomical and functional neuro-imaging techniques, as well as the development of neuropsychological models based on the face processing function, trying to discover not the brain structure responsible for the dysfunction, but the cognitive operation deficiency.
One of the first to emerge was Bruce and Young’s sequential model which stipulates that facial recognition progresses in three ordered steps. The first step is the encoding of general physical characteristics that are unique to this face. The next step is the comparison of this information with the memory stock of familiar people (composed of different Face Recognition Units or FRU), producing or not the feeling of familiarity. If the face is familiar, the final step consists of the stimulation by the FRU of the Person Identity Node (or PIN) containing the relevant semantic and biographical information. In Capgras delusion, the third step would be disturbed resulting in a dysfunction of the access to the sosified person’s PIN, the recognition of his face (steps 1 and 2) being preserved but not his identification. The familiar face activates the information related to the imaginary persecutor and not those of the real person.
In order to validate their model, Bruce and Young carried out research on soldiers with brain damage. The patients had issues specific to only a single area of the model, the rest remaining undamaged. For example, some of them could recognize a face but not where they knew it from. This experiment suggests that facial recognition is modular due to the damage only affecting one part of the process of face recognition. However, this model fails to explain covert recognition, the unawareness of where a perception of familiarity has come from, and furthermore indicates that it should not be possible. Capgras delusizon (CD) Essay.
This gave rise to Bauer’s two-route model which stipulates that there are two parallel pathways, instead of one in the first model, connecting the visual cortex to the limbic system (an association of cerebral areas believed to support emotion, behavior, and memory skills). The first is an overt ventral or primary route from the occipital cortex via the inferior longitudinal fasciculus to the temporal lobe and the amygdala which makes it possible to explicitly identify the observed face. The second is the covert dorsal or secondary route going from the occipital lobe to the superior temporal sulcus and the inferior parietal lobule which is responsible for the affective and unconscious recognition of the face.
In a 1990 paper published in the British Journal of Psychiatry, psychologists Ellis and Young, considering Bauer’s model, suggested that Capgras delusion could result from a dysfunction of the dorsal route with an intact ventral route (Ellis & Young, 1990, as cited in Henriet et al., 2008) which would make it the ‘mirror image’ of prosopagnosia, a disorder where patients are unable to recognize faces, even ones previously seen. Where in the former, patients are unable to covertly identify the face, in the latter patients are unable to overtly recognize faces. To verify that, skin-conductance responses SCR, a common physiological test used to measure the activity of the autonomic nervous system – a control system that operates unconsciously and regulates functions such as hear rat, digestion, or transpiration,… – was used. Bauer (1986) hypothesized that the autonomic response as a measure of unconscious or covert “recognition” of the familiar faces that is separate from conscious overt face recognition. Capgras delusizon (CD) Essay. After testing a group of CD patients CP, one of prosopagnosia patients PP and a control group, PP had larger responses whereas in CDP the responses did not differ when exposed to familiar vs unfamiliar faces. This means that prosopagnosia patients can covertly recognize familiar faces.(Tranel et al., 1985, Tranel and Damasio, 1985, Bobes et al., 2007). Another independent research group (Hirstein and Ramachandran, 1997) reported data consistent with the hypothesis and its implications. Together, these two conditions demonstrate a double dissociation between overt facial recognition and covert emotional processing of familiar faces, which in turn supports the existence of two distinct pathways: an overt one and a covert one.
However, the nature of this routes has yet to be defined. A study by Ungerleider and Mishkin (1982) on monkeys showed that the dorsal visual pathway was responsible only for the spatial location of an object and not its recognition. Milner and Goodale (1995) proposed that it was also the case of the human brain as well as an additional role of processing visually guided actions. However, that would imply that if, as they all argue, the ventral visual pathway is non-functional, then visual recognition must in some way be taking place in the dorsal visual pathway, which contradicts the studies. Therefore, due to the lack of evidence supporting the existence of two anatomical regions responsible for face recognition, Breen’s serial model came to be. This model agrees with the existence of two distinct cognitive routes however claims that the visual-limbic ventral route described by Bauer is the sole face processing area of the human brain. They argue that within this area there are two functional pathways from the Face Recognition Unit, one leading to the related Personal Identity Node, the other to an “affective response to familiar stimuli” module. According to the authors, Capgras delusion would be the outcome of a lesion or a dysfunction in the access to the additional module, whereas prosopagnosia would be the result of a dysfunction in the FRU or in the access to the associated PIN. This model can be interpreted in terms of intact ventral temporal visual recognition structures, including access to conscious recognition, but disrupted connections to the ventral limbic structures, or as impairment to the ventral limbic structures themselves, or a combination of these two, which furthermore agrees with Ellis and Young (1990)’s hypothesis that CD might arise from a loss of the normal affective response to familiar faces, without an impairment in face identification itself. This model is also more consistent with the analysis of Mesulan’ (1998) work (1990; Farah, O’Reilly, Vecera, 1993) that revealed weaker SCRs and longer reaction times in prosopagnosic patients which suggests that covert recognition is residual knowledge encoded in a damaged face recognition system that is then passed on as a low level input to the ventral limbic structures. (Breen N, Caine D, Coltheart M. 2000) Capgras delusizon (CD) Essay.
What the cognitive models have in abundance, the neuro-lesional models lack in prevalence due to how rare the condition. One study that compared the different neurological structures in a 71 CD patient with a control group of 10 men that had been screened to rule out any psychological or neurological disorder, used a modified t-test developed for single-case studies in order to examine the presence of a classical dissociation between the inferior fronto-occital fasciculus IFOF and inferior longitudinal fasciculus IFL counts in the patient with respect to the control-group. It revealed a significant decrease in the patient’s left IFOF and fiber counts, results that could be replicated in 2 additional studies conducted 6 months apart.
In the CD patient, the left IFOF was disrupted whereas the connections with the temporal lobe via the ILF survived. Thus, connections between occipital and frontal lobes were affected, with no damage to face specific functional areas. These results provide a neuroanatomical grounding of the cognitive models of face processing that emphasize the deficit in covert familiarity responses with intact overt person as a critical aspect of Capgras delusion (Ellis and Young, 1990, Breen et al., 2000a, Breen et al., 2000b, Ellis and Lewis, 2001). They posited the idea that Capgras delusion occurs when covert recognition system is impaired whereas the overt recognition system remains intact. These findings once more support the hypothesis and add to it that these two subsystems include either IFOF or IFL respectively as major highways connecting the frontal and occipital lobes as well as the occipital and temporal lobes respectively.
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Background: Capgras delusion (CD) has multiple etiologies including neurodegenerative disorders and can be associated with violent behavior. CD is a common complication of Alzheimer dementia (AD); however, CD with violent behavior is uncommon in AD. We report escalating violent behavior by a patient with advanced AD and CD who presented to the emergency department (ED) and required admission to an academic medical center.
Methods: Case analysis with PubMed literature review.
Results: A 75-year-old male with a 13-year history of progressive AD, asymptomatic bipolar disorder, chronic kidney disease, hypertension, hyperlipidemia, and benign prostatic hypertrophy presented to the ED with recurrent/escalating violence toward his wife, whom he considered an impostor. His psychotropic regimen included potentially inappropriate medications (PIMs) for geriatric/AD patients-topiramate/amitriptyline/chlordiazepoxide/olanzapine-that are associated with delirium, cognitive decline, dementia, and mortality. Renal dosing for topiramate, reduction in PIMs/anticholinergic burden, and substituting haloperidol for olanzapine resolved his violent behavior and CD.
Conclusions: CD in AD is a risk factor for violent behavior. As the geriatric population in the United States grows, CD in patients with AD may present more frequently in the ED, requiring proper treatment. Pharmacovigilance is necessary to minimize PIMs in geriatric/AD patients. Clinicians and other caregivers require further education to appropriately address CD in AD. Capgras delusizon (CD) Essay.