M6, T1, cognitive neuropsychology and delusions Flashcards
Cognitive neuropsychology
combination of both cognitive psychology and neuropsychology with emphasis on understanding the mind
Cognitive neuropsychiatry
applications of cognitive neuropsychology methods to understand/explain disorders of higher-level cognition
Delusions - APA
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 (APA, 2000)
Types of delusions
- Capgras Delusion
- Fregoli delusion
- Cotard delusion
- Somatoparaphrenia
- Delusion of Alien Control
What is a delusion
- A belief – A statement about the world the individual thinks it is true
- Based on inference – The belief doesn’t emerge from thin air – e.g. reasoning emerging following an abnormal perceptual experience
- The inference is incorrect – The reasoning used to form the belief is flawed
- It is a strongly held belief – Once established a delusion is very resistant to change
- It is culturally unusual – very few, if any, other people believe this in their culture.
Monothematic delusions
only concern a single topic
- This helps to pinpoint the cause of the delusion
- They are often caused by neurological damage
Encapsulated beliefs
do not interact with the rest of their beliefs
Capgras delusion (syndrome
- belief that someone emotionally close to you has been replaced by an imposter (Capgras & Reboul-Lachaux, 1924)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 monothematic delusion
- Suffers are delusional about a single issue. Other beliefs are normal
- Often the false belief is 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
Capgras case (Alexander, Stuss & Benson, 1979)
- 44 year 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
Capgras case (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 of Capgras delusion, Beheshti Hospital in Iran, extremely rare variant
- 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 delusions
- often specific to one person or set of persons
- Patient is convinced that although the person is identical to the original person in everyway, but 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
- 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).
Explanations for CD: neuropsychological, Joseph / Staton
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: cognitive neuropsychological, Hirstein and Ramachandran, 1997, affective integration model
- 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: cognitive neuropsychological, Ellis and Young 1990, affective response model
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 rationalisation strategy
*look up image
Explanations for CD: cognitive neuropsychological, Ellis 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
Issues with Ellis 1997, explanation for CD, cognitive neuropsychological
- Issue with Ellis et al (1997) study is the use of famous faces in the familiar condition
- Does the same ↑ SCR occur for familiar but not famous faces ?
- Case YY 20 year 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: cognitive neuropsychological, Breen et el., 2002, affective response model
-> Criticised 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: cognitive neuropsychological, Ellis and Lewis 2001, modified affective response model
- Ellis and Lewis (2001): modified affective response model
- Capgras patient lacks the autonomic response to a familiar face
- Capgras patient not consciously aware of what is different but “believes/feels” there is something different
- The delusional belief is a specific hypothesis to explain this difference
- Patient readjusts their belief to match their autonomic arousal level
*look up image
Explanations for CD: cognitive neuropsychological, Colheart et al. (2007, 2010, 2011) Two factor theory
- Capgras patient lacks the autonomic response to a familiar face (First factor)
- Damage to the right hemisphere (second deficit)
-> Right lateral prefrontal cortex
Role of the right hemisphere in CD
- 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?
Reviewing cases to determine role of right hemisphere
- 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)
