Week 10 - delusions Flashcards
What is a delusion?
A false belief based on incorrect
inference about external reality that is firmly
sustained despite what almost everyone else
believes and despite what constitutes
incontrovertible and obvious proof or evidence to
the contrary (DSM-IV, 2000).
What are 4 delusions covered in this course?
- Fregoli delusion
- Cotard delusion
- Somoatoparaphrenia
- Capgras Delusion
What is Capgras Delusion (syndrome)? (CD)
Capgras delusion (CD) is the belief that someone
emotionally close to you has been replaced by an
imposter (Capgras & Reboul-Lachaux, 1924)
• Father, mother spouse, children, pets, objects
CD is a___________ delusion
monothematic
sufferers are delusional about a single issue
Other beliefs are normal
The false belief is often ______?
encapsulated
Sufferer doesn’t wonder why the family has been
replaced
• CD sufferer not aware their belief is a delusion but
often have a sense that what they believe is odd
• CD not that rare
Case Capgras (Alexander, Stuss & Benson, 1979)
44 yr old male, road accident victim
• bilateral lesions frontal lobe
• extensive right hemisphere damage
• Prior to accident – auditory hallucinations and
delusions following prolonged period of stress but
never acted on them
• Over 2 years after accident reported that he had
two families
Case Capgras (Alexander, Stuss & Benson, 1979) • In each family
• wife same name, similar appearance and manner
• 5 children same names, gender but thought original
family one year younger
• claimed change occurred in Dec 1975 (one month after
accident) when his new wife came to pick him up from
hospital (sig not told going home?)
• Reported he had not seen original family since then but
positive feelings towards both wives
• Although he believed this implausible was unable to
change beliefs
Another example
• Researchers at the Beheshti Hospital in Iran reported an
extremely rare variant of Capgras syndrome in which a
55-year-old woman with epilepsy believes her
possessions have all been replaced by substitute objects
that don’t belong to her.
• When she buys something new, she immediately feels
that it has been replaced.
• However, the authors reported there was no evidence of
dementia, her memory was intact, and her immediate,
recent, and remote memories were okay.
• She was oriented to time, place and person, and had
appropriate intelligence.
• She also had no history of head injury or migraine, and
brain scans revealed no gross abnormality.
Consistent features of Capgras
• Delusion often specific to one person or set of persons
• Patient is convinced that although the person is identical to
the original person in everyway they are different
• Belief resistant to criticism, however patients can recognise
the idea is absurd
• False person is never mistaken for someone else or given a
different name
• Patient cannot explicitly identify the differences between the
current and true person
• Delusion tends to occur in familiar contexts (home)
• Patients adapts well to imposter
When does Capgras delusion occur?
• Usually with a psychiatric illness • Organic illnesses • Neurological damage • Examples • 4% psychosis patients • Mostly paranoid schizophrenia • Schizoaffective and affective disorders • Alzheimer’s disease (20-30%) • Epilepsy, tumours, head injury, multiple sclerosis, Parkinson’s disease and so on
Explanations for CD: Psychodynamic
Oedipal interpretation - if one’s mother is not
actually one’s mother but an imposter then sexual
feelings towards her don’t allow you to feel guilty
(Capgras & Carrette, 1924)
• Feelings of hatred or aggression toward to a
spouse may make you feel guilty, and the
formation of a believe that the person at who
these feelings after directed it is not the spouse
but some stranger will remove this guilt (Enoch &
Trethowan, 1979).
• Defence against incestuous or hostility issues in
women
• Latent homosexuality in males
Explanations for CD: Neuropsychological
Joseph (1986): cerebral hemisphere disconnection
hypothesis
• Each hemisphere independently processes visual
information about faces
• Capgras delusion occurs when the two sets of
information fail to integrate
• Staton et al (1982): failure to update patient’s
mental representations
• Capgras due to mismatch between what is
currently seen and the memory representation
Explanations for CD: Neuropsychological
• Ellis et al. (1997)
• Normal participants view pictures of familiar faces
this generates a strong autonomic response
(SCR) compared to the autonomic response
generated for unfamiliar faces
• Capgras patients have weak autonomic
responses that do not depend on the familiarity of
the facial stimulus
• Capgras patients can recognise faces
• It appears that there is a disconnection between
the face recognition and the limbic system
Explanations for CD: Neuropsychological
• Ellis and Young (1990)
• Normal face processing – dual route (Bauer, 1984)
• Ventral route – seeing a face allows you to
recognise a familiar person
• Dorsal route – affective response to the face
• Prosopagnosia – damage to the ventral pathway
• Capgras delusion – damage to the dorsal
pathway
• Lack of affective response conflict within the
person they adopt a rationalization strategy
Explanations for CD: Neuropsychological
• Issue with Ellis et al (1997)
is the use of
famous faces in the familiar condition
• Does the same ↑ SCR occur for familiar but not
famous faces ?
• Case YY 20 yr old female with Capgras for her
father (Brighetti, Bonifacci, Borlimi & Ottaviani,
2007)
• YY - no SCR differences for pictures of family and
strangers but she could correctly identify the faces
as known/unknown to her
• Control showed greater SCR to familiar faces than
unfamiliar faces
• SCR (limbic) and face recognition disconnection
still holds
Explanations for CD: Neuropsychological
• Hirsten & Ramachandran (1997)
• Capgras due to a failure to process information
between the face-processing components of the
temporal lobe and limbic system
• Capgras – failure to integrate ongoing memories
of a person across episodes
• Damage prevents patient from integrating current
encounter with person to the stored “file” on that
person and so creates a new file
• Limbic activation (emotion) acts as a glow to help
link successive episodes with that person
Explanations for CD: Neuropsychological
• Breen et al (2000) – criticized Bauer’s account
• Structures within the dorsal route guide actions not the
recognition of objects
• Unlikely that this pathway has structures capable of
face recognition or a production of an affective
response in relation to familiar stimuli
• Face recognition occurs via the ventral pathway
and affective responses to faces are provided by
ventral limbic structures including the amygdala
• Model explains both Capgras delusion and
Prosopagnosia
• Model does not explain how a lack of affective
response to becomes a delusion
Explanations for CD: Neuropsychological
• To account the lack of autonomic response to the
a familiar face a Capgras patient may believe that
the person I am seeing is not my significant other
but is someone else which is why I no longer
have the same level of autonomic response that
used to occur
• Capgras not consciously aware of what is
different
• Patient readjusts their belief to match their
autonomic arousal level
Explanations for CD: Neuropsychological
• Coltheart et al
• Although the lack of arousal responses to faces is
necessary for Capgras it is not sufficient
• Patients with damage to ventromedial regions of
the frontal cortex show this lack of arousal to
familiar face but are not delusional (see Tranel,
Damasio & Damasio, 1995)
• A second deficit must be present to account for
the failure to reject the belief that results from the
SCR deficit (first deficit)
• Damage to the right hemisphere (second deficit)
Explanations for CD: Neuropsychological
• What is the role of the right-hemisphere (RH) in
Capgras delusion?
• Ellis and colleagues – damage to the RH impairs
face perception
• But Capgras delusion occurs for the voice of a
family member and for objects
• Coltheart et al. – RH damage impairs belief
evaluation
• Is there any evidence? Where is the lesion
located?
• Is there any evidence? Where is the lesion
located?
• Review of 22 cases of delusions – 18 cases
damage right frontal lobe, 2 cases diffuse bi-lateral
damage (Burgess, Baxter, Rose & Alderman (1996)
• ERP study of delusional patients, found that the
P300 component was reduced in the patients
compared to controls in the right frontal region
(Papageorgiou et al, 2003)
• Delusional and non-delusional patients with
Alzheimer’s disease – delusion patients had
reduced activity in the limbic and right frontal
regions compared to the non-delusional group (Staff
et al 1999)
Patient had tumour removed from right frontal
sagittal area Capgras delusion stopped (Fennig,
Naisberg-Fennig & Bromet, 1994)
• Evidence points to right frontal lobe playing a role
in belief evaluation
Explanations for CD: Neuropsychological
• Luccehlli & Spinnler (2007) – Capgras is a cross
modal disorder
Capgras occur with multi-modal interaction
• Capgras failure of person not face recognition
Organic evidence for Capgras
• Right hemisphere lesions
• Also bi-lateral damage in most patients
• Main areas of damage – frontal, temporal or
parietal lobes
• CT scans more extensive bi-lateral frontal and
temporal atrophy in schizophrenic patients with
Capgras than in those without Capgras
• PET abnormal brain glucose metabolism in
paralimbic structures and temporal lobes in
patients with Alzheimer’s and Capgras
• Neuropsychological tests show patients have
affected frontal lobe functioning
