Descriptive Psychopathology: The Signs and Symptoms of ...

255 Chapter 10: Perceptual disturbancespeople seem darker than in fact. In digitalis toxicity, green hues predominate.In caffeinism, blue or yellow hues predominate. In migraine, colors may fade andthe environment appears gray. 9IllusionsIllusions are false perceptions or misinterpretations of environmental stimuli.They arise from a lack of perceptual clarity resulting from diminished or ambiguousstimuli or from perceptual distortion due to intense emotion. Non-ill personsexperience illusions. “Seeing” a “face” or other recognizable images in a cloud isillusory when the experience is intense (a pareidolic illusion). Non-ill persons alsoexperience illusions when clarity is diminished as at night and when anxiety isheightened as when walking down a dark street and perceiving a swaying bushbehind a tree as a crouching figure.Delirium and manic-depressive illness are conditions that diminish perceptualclarity and elicit illusions. In delirium, innocent gestures by hospital personnelmay appear threatening. Depressive delusions distort the interpretation of soundsand gestures as dangerous or as confirmation of misdeeds. Manic patientsperceive car horns as heavenly trumpets and interpret adoration or jealousy inthe faces of passers-by. Patients exhibiting persecutory delusions and experiencesof self-reference detect conspiracies in the innocent gestures and conversationsof persons who are nearby. Patients with schizotypal illness misperceive objectsin their peripheral visual field as scurrying animals, supernatural creatures, orbody parts.Auditory illusions usually involve mishearing speech, the distortion oftenshaped by the person’s emotional state. Tactile illusions are rare and typicallyrelate to temperature, the weight of objects, or the character of surfaces. Gustatoryand olfactory illusions are also rare and vaguely unpleasant. 10Fantastic illusions are perceived extraordinary modifications of the environment.The psychopathologist Frank Fish refers to a patient of Griesinger’s wholooked in the mirror and saw his head as that of a pig. Fish describes his ownpatient who during an examination saw Fish’s head change into a rabbit’s head.The patient also expressed fantastic confabulations. 11 Muller–Lyer illusions referto perceptions that do not agree with the physical stimulus (e.g. Fish’s patient).Fantastic illusions are forms of misidentification, and when present suggest rightcerebral hemisphere disease.Psychosensory phenomenaPsychosensory phenomena differ from other perceptual disturbances in that theyare brief (rarely longer than a minute), intense and paroxysmal, and repetitive.