Descriptive Psychopathology: The Signs and Symptoms of ...

273 Chapter 11: Delusions and abnormal thought contentSources of delusional developmentLike perceptual dysfunctions that may arise from disease anywhere along thesensory pathways, the pathophysiology of delusions may begin at any level ofthe nervous system that ultimately leads to an articulated conclusion of thought.While the neuropathology of the process is unclear, the progression to thedelusional conclusion is distinguishable.Perceptual disturbanceDelusions that arise from other psychopathology are defined as secondarydelusions. The delusional process begins with the sufferer perceiving the immediateenvironment in such a way that the delusional conclusion is inescapable. Hollywoodoffers examples of this in films about the supernatural and extraterrestrials.The images on the screen are compelling, and the audience is frightened. Thefalse images trigger a physiological flight/fight response over-riding corticalmodulation of the sham. The experience is emotional, not initially cognitive asaudience members are fully aware of the subterfuge.Persons in other settings experiencing equally powerful but false perceptions oftheir immediate environment (i.e. hallucinations or perceptual distortions) will alsobe frightened. Intense and prolonged false perceptions over-ride cortical modulationand, despite the protestations of others, the experience elicits false conclusions basedon “I saw it with my own eyes”. The delusional process unfolds, the false perceptioneliciting a strong emotional response compromising judgment and self-assessment,which in turn results in a false but inescapable delusional conclusion. The falseperception, however, need not be as dramatic as film images. The initiating perceptualdisturbance needs to only be sufficient to trigger an emotional response strongenough to overcome judgment, accepting the false interpretation of the experience:“it’s real and dangerous” rather than “I’m hallucinating”. This mechanism has beenproposed to explain the delusions in persons with schizophrenia. 3 Capgras, Fregoli,and delusions of misidentification (see below for definitions) can also be understoodas reflecting an initial problem with perception.The idea that subtle perceptual disturbances underlie delusional formation issupported by studies that report that delusions are not always directly linked tocognitive disturbance. 4 Patients with schizophrenia, the most common diagnosticclass studied, also have subtle perceptual problems associated with delusions.Deficits in processing the Gestalt of stimuli (e.g. shape, size, identity of theobject), 5 and lateralized abnormal perceptual experiences 6 in patients withschizophrenia are particularly relevant because these visual perceptual problemsare similar to those seen in patients with right cerebral hemisphere disease andassociated delusional symptoms. 7