ABSTRACT
Observations on a man with dementia who presented with episodes of delusional misidentification of short duration that could be terminated by a specific psychological event, lead to the development of a model of delusional misidentification which attempts to explain how organic cerebral disorder and psychological forces may interact with one another to produce the symptom. The model relies on the susceptibility of preconscious perceptual processes to the “top-down” influence of expectations and preconceptions. A positive feedback loop therefore exists which may enable abnormal beliefs to distort perceptions in such a way as to reinforce the abnormal belief: this may result in a delusional misidentification. Good perceptual and mnemonic processing, unimpaired by organic cerebral disorder, will reduce the likelihood of this happening. Therefore either powerful psychic forces, particularly paranoia, and/or organic cerebral disorder may produce a delusional misidentification. The model predicts that, across a population of patients with this symptom, there will be an inverse relationship between the strength of organic cerebral disorder evident within an individual, and the likelihood that they will have paranoid delusions preceding the onset of the delusional misidentification. The model also draws attention to the possibility that the reasoning strategies which may be involved in normal belief formation are similar to those that take place, preconsciously, during perceptual processing. It is therefore possible that patients with delusions who tend to “jump to conclusions” may also be liable to “jump to perceptions”, and thereby be prone to delusional misidentification.
