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delusional misidenfication syndromes - Coggle Diagram
delusional misidenfication syndromes
capgras syndrome
what is it
patient may see themselves as their own double
these feelings may drive psychotic behaviour, DMS are a risk factor for potential violence towards others (silva et al., 1996)
person might be conscious of the abnormality of these perceptions, there is no hallucination suggesting this not a psychotic disorder
syndrome is not limited to people as patient David could not recognise is own house, also documented for pets which discounts the freudian explanation
the message gets to the temporal lobe, can retrieve the right information to recognise the object/stimulus but the message does not reach the amygdala so patient does not access the emotional warmth that would be associated with the stimulus
recognises the imposter but they are psychologically different
the double is usually a key figure for the person at the time of onset of symptoms
causes of capgras syndrome
ellis and young (1990)
hypothesised that p's with capgras delusion may have mirror image of prosopagnosia (double dissociation)
conscious ability to recognise faces was intact but they might have damage to the system that produces the automatic emotional arousal to familiar faces
might lead to the experience of recognising someone while feeling something was not quite right about them
prosopagnosia = no overt recognition but some covert recognition
capgras syndrome = has overt recognition but no covert recognition
two route neuroanatomical model (bauer, 1984)
overt recognition = ventral visual limbic pathway
covert recognition = dorsal visual limbic pathway (affective)
ellis and young (1990) suggest that prosopagnosia = damage to ventral route (cases with no overt or covert have damage to both pathways) and capgras = damage to dorsal route
supporting evidence
capgras patients recognise familar faces but do not generate autonomic responses to known faces (ellis & young, 1990)
in prosopagnosia patients did produce a SCR shower preserved covert recognition, the opposite is found in capgras
ellis et al (1997)
capgras p's did not achieve autonomic discrimination between familiar and unfamiliar faces
prosopagnosic p's with preserved covert recognition would see the same pattern as controls
breen, caine & coltheart (2000)
proposed a single neuroanatomical route for face recognition = ventral
the operation of ventral route and its connections with the amydala can account for prosopagnosia and DMS
model is on slide 23: explains how capgras can have facial recognition and name generation but no emotions
model does not explain how some prosopagnosic p's get stuck on face recognition units but still produce an affective response to stimuli
ellis and young (2001)
suggested that a loss of emotional responsiveness alone cannot underpin capgras for example: lots of brain injured p's suffer from problems with emotional responsiveness but do not have capgras
they added an integrative device to model which compares output from identification and affective routes: capgras is when the integrative device does not receive the expected emotional response to a familiar face
lesion sites
A: beween FRU and PINs = prosopagnosia
B: between FRU and affective response to familiar stimuli = capgras
C: between affective response to familiar stimuli and SCR = not a result in capgras, explaining brain damage p's who don't suffer with capgras but have problems in emotional responsiveness
darby et al (2017)
lesions in one brain region may disrupt brain acitivity in other parts of the brain as well
used relatively new technique called lesion network mapping which determines areas that are functionally connected to the location of a focal brain injury
found that lesions causing delusional misidentifications in different locations had the same pattern of brain connectivity
all the lesions causing delusional misidentifications were connected to regions involved with familiarity
16/17 p's had lesions coneected to regions involved in evaluating beliefs
non-face specific accounts of DMS
rojo et al. (1991)
blind p's believe people/pets to be replaced by imposters = no affective response to familiar voices?
lewis & sherwood (2001)
patient HL = not blind but only capgras delusion to voices
suggests modality specific pathways to faces and voices
misidentification syndromes
variety of disorders which share the common feature of mistaken belief in identity of oneself, others, places or objects
due to malfunction in familiarity processing
types of syndromes (christodoulou, 1978)
hypo-under-identification (capgras)
hyper-over-identification (fregoli syndrome, intermetamorphosis, subjective doubles)
psychiatric or organic etiology
majority of MS reported as psychiatric
significant proportion of p's found to have some brain lesion
signer (1994) found 35% of 570 cases of Capgras syndrome had organic etiology
weinstein (1996) found brain tumor, aneurysm, stoke, epilepsy, alzheirmers and other lesions
solla et al. (2017) found dementia with lewy bodies
aetiology
evidence that right hemsiphere underpins DMS, particularly FL
Forstl et al. (1991) had 19/20 cases with DMS had right sided abnormalities
feinberg et al. (2005) 29 cases of DMS had 0 unilateral left lesions
fregoli syndrome
first reported in 1927
classed as a monothematic delusion
others in the environment are perceived correctly as being physically unrecognisable strangers or casual acquaintances but are incorrectly identified as a different known person
cannot be explained through overstimulation hypothesis because there are 1-1 mappings of stranger and familiar face misidentification
delusional belief that different people are in fact a signle person who changes appearance or is in disguise
syndrome might be related to brain lesion and is often paranoid in nature with the person believing they are being followed by the person they believe is in disguise
hyper-identification
explanations
PIN driven by malfunctioning cognitive systems (can see difference between faces but it is driving the same PIN)
nodes hyperexctable & imparied decision making mechanisms accept this identification (so multiple faces excite the same node for a familar face)
intermetamorphosis
physical appearance of someone may change radically to correspond with the appearance of someone else
courbon & rusques (1932) critique this as its own separate disorder and instead a varaint of Fregoli (review article by langdon et al., 2014)
p's believes that certain individuals interchange with one another, taking psychological and physical similarities rather than being in disguise
bick (1986) 3/4 reported cases have temporal lobe epilepsy (organic origin)
explanations
inappropriate excitation of an FRU (lower triggering threshold)
FRUs signal familiarity which communicate with PIN to retreive biographic details of person
can create a percept of the face but the FRUs are misfiring allowing the face to change (different to prosopagnosia as they cannot create a percept of the face)
FL dysfuntion may controbute to misattribution of identity, this is often associated with epilepsy
subjective doubles
commonly occurs alongside capgras
p's believe that their double has a different personality
p's can believe that all or part of their personality has been transplanted into the double
silva & long (1991) is a good example of this disorder
lycanthropy
belief in human metamorphosis into animal form
metamorphosis occurs on patient rather than another person
causes of DMS
L-DOPA
used to treat parkinson's disease and dopamine responsive dystonia
can lead to visual hallucinations and delusions
is most common cause of fregoli due to anti-parkinsonian meds
traumatic brain injury
injury to right frontal and left temporoparietal areas can cause fregoli
executive dysfunction might be necessary to identify one as having fregoli syndrome
self-monitoring, mental flexibility and social reasoning
lesions
lesions to right TL and FFA may contrbitue to DMS
brain thought to interpret visual scenes through dorsal (where) and ventral (what) pathways
abnormal P300
DMS occur due to dissociation between identification and recogniton (working memory)
P300 is an index of WM and DMS p's found to exhibit an attenuated amplitude and prolonged latencies of P300
findings suggest DMSs are accompanied by abnormal WM specifically affecting PFC (papagerogiou et al., 2002)
cortard's delusion
delusion by a living person that he or she is dead
doubt their own existence and existence of external world
explanations
ramachandran & blakeslee (1998): more severe form of capgras delusion, involving damage to more neural pathways
young & leafhead (1996): propose it is a matter of attribution differences; people who are internally focused are more like to experience cotard's and people who are externally focused more likely to experience capgras