Once manifested, the images may last for periods varying from seconds to minutes to hours. Triggers of the syndrome include fatigue, low levels of illumination, bright lighting and stress (as with this patient). In 1760, Charles Bonnet described vivid visual hallucinations in his psychologically normal visually impaired grandfather. The phenomenology of the visual hallucinations does not appear to correlate with the underlying ocular disease, although significant bilateral loss in visual acuity appears to be a primary trigger. The content of the visual hallucinations range from colored shapes and/or patterns (simple visual hallucinations) to well-defined recognizable forms such as faces, animals, objects and scenes (complex visual hallucinations). When visual hallucinations follow marked visual acuity loss, in the absence of cognitive impairment, the condition is termed Charles Bonnet Syndrome, with an estimated prevalence of 0.5–17%. Visual hallucinations have been reported in patients with impaired vision or blindness since birth. In the above conditions the modality and content of hallucinations depends on the area of the brain involved. Systemic lupus erythematosis (SLE), which involves the central nervous system, may present as hallucinations. Hallucinations have been reported in sleep disorders such as narcolepsy. ![]() These complex visual hallucinations arise due to lesions that straddle the cerebral peduncles or involve the medial substantia nigra pars reticulata, bilaterally. Peduncular hallucinations produce vivid, non-stereotyped, continuous, gloomy or colorful visual images that are more pronounced in murky environments. “Crude” auditory hallucinations are more common in these conditions than formed ones. ![]() Olfactory hallucinations and gustatory hallucinations are usually associated with temporal lobe lesions and lesions in the uncinate gyrus. Hallucination in neurological and organic mental disordersįormed and unformed visual hallucinations occur as a result of cortical lesions involving the occipital and temporoparietal areas. This phenomenon can occur months after the last intake of drug. After repeated ingestion of drugs, some people may experience a phenomenon called “flashbacks,” which are spontaneous recurrences of illusions and visual hallucinations during the drug-free state, similar to that experienced during the active stage of drug administration. Reflex hallucinations are experienced under the influence of psychedelic drugs, wherein the patient perceives colorful visual hallucination in response to loud noises. Tactile hallucinations in the form of insects crawling up the skin are experienced during cocaine and amphetamine intoxication. Auditory hallucinations that are unformed and indistinct noises are heard in substance-induced psychoses. Later on, the person experiences vivid and colorful images. The images are usually abstract, such as lines, circles and stars. These are usually preceded by unformed visual sensations – alterations of color, size, shape and movement. Psychoactive substances predominantly induce visual hallucinations. Hallucinations induced by psychoactive substances Lights, visions and voices may be seen or heard during profound religious or mystical experiences, especially conversion – the experiences of Joan of Arc and St Paul are familiar examples. Up to one in six people in Britain and the United States have seen, heard or otherwise experienced ghosts or spirits. Recently, bereaved widows and widowers may “hear” or, more commonly, “see” their dead spouse. A few people describe hearing a comforting or advising voice at some time in their lives. Hearing one's name called aloud or hearing a person's voice but finding no one there is common. Although hallucinations have been a hallmark of mental illness for centuries, they are not always pathological. This paper attained cult status as a paradigmatic case throughout the psychological literature of the nineteenth century following its translation into English in 1803. This apparition haunted him for the duration of the day and, in the subsequent weeks, the number of these figures began to increase. ![]() In 1799, a Prussian bookseller of skeptical disposition named Christoph Friedrich Nicolai read a paper to the Royal Society of Berlin entitled “A Memoir on the Appearance of Spectres or Phantoms occasioned by Disease.” In this, Nicolai described how one morning in February 1791, during a period of considerable stress and melancholy in his personal life, he saw the apparition of a deceased person in the presence of his wife, who, however, reported seeing nothing.
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