Abnormalities of Thought Content
Several disorders are virtually defined by the presence of abnormalities of thought content. In many instances the patient will complain of these phenomena (eg, a phobia of heights); in other cases the patient appears to have accepted an eccentric idea (eg, the delusion of being a reincarnation of Christ) and to be acting accordingly. Abnormal thought may be divided into the following categories: abnormal perceptions, abnormal convictions, abnormal preoccupations and impulses, and abnormalities in the sense of self.
Abnormal Perceptions
Perception is physical sensation given meaning, the integration of sensory stimuli to form an image or impression, in a manner or configuration influenced by past experience. Perception may be increased or decreased in intensity. Heightened perception occurs in delirium, mania, after hallucinogens, and in the rare ecstatic states that occur as part of acute schizophrenia or “transported” hysterical trances. Dulled perception occurs in depression and organic delirium.
In derealization, the external world seems different, changed, vague, unreal, or distant. This symptom is common in adolescence, in association with depersonalization. It is also associated with anxiety or dissociative disorders, depression, schizophrenia, organic brain disorder, and after hallucinogen use. In synesthesia, the subject perceives color in response, for example, to music. It is a common psychedelic experience.
Time may be experienced as accelerated under the influence of hallucinogens, in mania, or during an epileptic aura. Time may seem slowed or stopped in depression or epilepsy. In some conditions, time seems to lack continuity and the subject feels uninvolved in the temporal stream. This is particularly likely to be encountered in depersonalization, amnestic syndromes, depression, schizophrenia, or toxic-confusional states.
An illusion is sensory stimulation given a false interpretation, that is, a false perception. Illusions are most likely to occur when the mind is under the sway of an emotionally determined ideational “set” (eg, vigilance for an intruder), when sensory clarity is reduced (eg, at night), or when both sets of circumstances are operating (as when a frightened elderly patient has both eyes bandaged following ophthalmic surgery). Illusions are common in delirium and may be visual (eg, fluttering curtains seen as intruders), auditory (eg, a slamming door interpreted as the report of a pistol), tactile (eg, skin sensations thought to be caused by vermin), gustatory (eg, poison detected in the taste of food), kinesthetic (eg, flying), or visceral (eg, abdominal pain thought to be caused by ground glass). Illusions may also occur in hysteria, depression, and schizophrenia, particularly when perception is subordinated to a delusional idea (eg, of guilt or persecution) or an emotion of great force (eg, abandonment or erotic yearning).
A hallucination is a false perception that occurs in the waking state in the absence of a sensory stimulus. It is not merely a sensory distortion or misinterpretation, and it carries a subjective sense of conviction. A true hallucination appears to the subject to be substantial and to occur in external objective space. In contrast, a mental image is insubstantial and experienced within internal subjective space. Deafness, tinnitus, or blindness, usually in association with dementia or delirium, may determine the modality of hallucinations.
Sensory deprivation experiments have produced visual and auditory hallucinosis in many subjects. Hallucinosis and delirium following cataract operation probably acts by the same mechanism, especially in association with dementia. Diencephalic and cortical disease may be associated with hallucinations (usually visual). Tumors of the olfactory or basal temporal regions may cause olfactory hallucinosis, for example, as an aura. Hallucinations, especially visual (though sometimes vestibular and kinesthetic), are common in the delirium caused by toxins (eg, drugs, hallucinogens, alcohol, toxins), fever, cerebrovascular disease, and central degenerative disorders. Hallucinations may also be a prominent feature of the uncommon schizophrenia-like psychosis associated with epilepsy. Aside from these medical circumstances, hallucinations are common and normal, especially in some people, when falling asleep (hypnagogic) or waking (hypnopompic). Severe sleep deprivation can cause hypnagogic hallucinosis.
Hallucinations can be auditory, visual, olfactory or gustatory, tactile, or somatic. In form, they may be amorphous, elementary, or complex. They may be experienced as emanating from inner or outer space and, if from outside, from near or far. Hallucinations may be unsystematized, appearing to have no link to life circumstances, or systematized and part of a causally interconnected delusional world.
Auditory hallucinations may be inchoate (eg, humming, rushing water, inaudible murmurs), fragmentary (eg, words or phrases such as “fag,""get him,” or “beastly") or complex. Typically the schizophrenic patient locates complex hallucinations in inner or outer space, as a voice or voices speaking to or about him or her. The voice may be soothing, mocking, disparaging, or noncommittal. Sometimes the voice echoes the patient’s thoughts or comments neutrally on his or her actions. Sometimes the voice orders the patient to perform actions, or puts thoughts into his or her head, a notion verging on thought insertion. The voice may be perceived as coming from the radio or television, from outside the window, or even from a distant place. In alcoholic hallucinosis, typically, a conspiracy of threatening whisperers plan to injure the patient, provoking the patient to defend himself or herself or to take flight.
Visual hallucinations vary from elemental flashes of light or color, as in disorders of the visual pathways and cortex, to well-formed scenes of people, animals, insects, and things. In delirium, insects or other small objects may be seen moving on the bed or in the surroundings. Lilliputian hallucinations, of little people on the bed, for example, occur in delirium and other organic brain syndromes. Complex audiovisual hallucinations may occur in temporal lobe epilepsy. In general, visual hallucinosis suggests acute brain disorder rather than functional psychosis and tends to occur in a setting of confusion or obtundation. Sometimes, however, a schizophrenic patient will report visual hallucinations (eg, trips in flying saucers) aligned with his or her prevailing delusions. The visual hallucinations of hysteria or dissociative disorder have a pseudo-hallucinatory quality and sometimes represent a traumatic event, as when a war veteran relives a battle incident.
Olfactory and gustatory hallucinations (eg, burning rubber, steak and onions) may occur in epilepsy. Schizophrenic patients may perceive gas being pumped into their bedrooms by persecutors or may think they taste poisonous substances in their food. Melancholic patients may be conscious of the stench of corruption rising from their unworthy bodies or may complain of the changed, metallic, tasteless quality of their meals.
Tactile hallucinations are characteristic of cocaine and amphetamine intoxication, the patient being distracted by the sensation of insects crawling on the skin. Schizophrenic patients may detect the effect on the skin of radioactivity beamed at them from a hostile source.
Somatic hallucinations occur in schizophrenia, whereby genital, visceral, intracerebral, or kinesthetic sensations are often referred to the influence of persecutors or machines. The melancholic patient may have the sense of having no stomach, with food dropping from the throat into a void.
In schizophrenia, or under the influence of hallucinogens, the patient may have the uncanny sense that somebody, a presence, is behind him or her. This can occur in states of extreme fear, but it may become a central feature of schizophrenia, in the guise of the doppelga"nger or Horla, a hallucinatory double of the self who always lurks just behind the periphery of vision.
