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The cognitive neuropsychiatry of delusional belief.

Sunday, October 02nd,   2011 [11:30 - 13:10]

SY_32. The cognitive neuropsychiatry of delusional belief

Coltheart, M.

Centre for Cognition and its Disorders, Macquarie University, Sydney, Australia

Cognitive neuropsychiatry is a relatively new branch of cognitive neuropsychology that investigates higher-order cognitive processes such as belief formation, the sense of agency, self-knowledge, and emotion, via detailed studies of people with impairments of such cognitive processes. That is, cognitive explanations of psychiatric symptoms are sought. Just as acquired dyslexia was the major topic for cognitive neuropsychology in its early years, so delusional belief has been the major topic in the initial years of cognitive neuropsychiatry. The four speakers at this symposium will discuss the current state of the cognitive-neuropsychiatric understanding of a variety of delusional beliefs such as Capgras delusion ("My wife has been replaced by an impostor who looks just like her"), Fregoli delusion ("I am being constantly followed by people I know, whom I cannot recognize because they are always disguised"), Cotard delusion ("I am dead"), the delusion of alien control ("Other people can cause parts of my body to move, against my will"), and shared delusions such as the mass hypochondria present in cultures affected by Koro syndrome (the belief that one's sexual organs are shrinking and will disappear). Laboratory research within the frameworks of behavioural economics and of associative learning that bears upon the cognitive explanation of delusional belief will be presented, as will psychopharmacological research concerning the model psychosis produced by administration of ketamine.



SY_32.1 - Delusional beliefs: a two-factor cognitive theory

Coltheart, M.

Centre for Cognition and its Disorders, Macquarie University, Sydney, Australia

According to the two-factor theory of delusion, to explain any particular form of delusional one needs to provide answers to just two questions. First: why did a belief with this particular content ever occur to the deluded person in the first place (for example, what made a patient with Cotard delusion ever entertain the thought that his wife has vanished and been replaced by an identical-looking impostor)? Second: once the delusional idea does come to mind, why is it accepted as a belief, rather than rejected (as it should be, given that most delusional beliefs are so bizarre, and given that the patient's family, friends and clinicians are all denying the truth of the belief)?

An account will be given of how this theory is applied to the explanation of a variety of delusions will be given, and current difficulties for this account will be discussed.

SY_32.2 - The two-factor approach to delusional belief and the distinction between immediate and reflective delusions

Langdon, R.

Centre for Cognition and its Disorders, Macquarie University, Sydney, Australia

Inspired by the idea that delusions begin when a person reflects upon a disquieting experience and searches for explanatory hypotheses, researchers have focused on the role of reasoning biases in delusional formation. But such biases are not always present in delusional people. Moreover, the reflective explanation has difficulties in accounting for the incorrigibility and unwarranted subjective conviction of delusions. An alternate approach fares better here On this alternate approach, the explanation of anomalous data proceeds largely unconsciously and outputs fully-formed delusional content directly to consciousness, where it is endorsed as representing reality. Neither approach accounts satisfactorily for all delusions. I suggest, instead, an "immediate-reflective" spectrum. At one pole of this spectrum are immediate delusions with content that arises fully-formed and fully-(mis)believed in consciousness. At the other pole are reflective delusions that arise after reflection upon a disquieting experience, and for which the crystallisation of delusional conviction is more gradual.

SY_32.3 - Shared delusions

McKay, R.

Department of Psychology, Royal Holloway University of London, Egham, UK

Deluded individuals hold beliefs unwarranted by available evidence and jeopardizing their prospects in some way. Such beliefs can stem from clinical abnormalities in cognitive processes, but may also arise via ordinary operation of such processes, coupled with the social diffusion of information. Examples include cases of mass hypochondria (e.g., epidemics of Koro, the belief that one's genitals are retracting into one's body). We call such examples \"shared delusions\". We allowed participants to learn from each other in the face of a common uncertainty, state-dependent error costs, and a subtle framing manipulation activating the concept of intentional agency. In the end, incorrect choices often spread in social groups. The result was a profusion of persistent, error-prone social traditions involving choices resulting in substantial losses. Such traditions may not quite qualify as delusions, but do represent collective errors, transmitted from one person to another, with potentially far-reaching social, political and economic repercussions.

SY_32.4 - Rendering delusions understandable through cognitive neuroscience

Corlett, P.

Department of Psychiatry, Yale University, New Haven, USA

Prediction error is the mismatch between expectation and experience, used as a teaching signal to update beliefs and an impetus to allocate attention toward potential explanations. Delusions could result from aberrant prediction errors, specified inappropriately, driving attention toward irrelevant stimuli, thoughts and percepts and forging the formation of odd and unusual beliefs. I will outline evidence favoring this model from functional neuroimaging studies of causal belief formation in patients with endogenous psychosis and healthy individuals exposed to a pharmacological "model psychosis"; the drug ketamine. A crucial feature of delusions is their tenacity. This feature may well also be explicable in terms of aberrant prediction error. Surprising events demand change in expectancies, necessitating making what we have learned labile and so updatable: updating, binding memories anew (memory reconsolidation). Under the influence of excessive prediction error, delusional beliefs may be repeatedly reconsolidated, strengthening them so they persist, impervious to contradiction.

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