A patient with a perceptional disorder is able to see an object without any external stimulus. This phenomenon is known as:

Ans: B (Hallucination) Ref: Kaplan and Sadock's Comprehensive Textbook of Psychiatry. 9th editionExplanationPsychiatric symptoms can be approached as per computer model of mind which divides mind into three components -1. Input (sensation and perception).2. Output (speech and motor activity).3. Central processor (comprising Consciousness, Cognition and Feelings).Perceptual problems are two:1. Illusion - Where a person perceives an object as a different one. For example, perceiving rope as a snake.2. Hallucination - Where one perceives an object when there is nothing i.e., no external stimulus at all (as in the question).* Both illusion and hallucination have sub-types, based on the modality.1. Visual2. Auditory3. Gustatory4. Olfactory5. Tactile6. Others.IllusionCan be a normal phenomena like:o Falling asleepo Waking from sleepo Fatigue stateso Grief reactionIllusion can be abnormal as in:o Deliriumo Acute stress reactiono Post-traumatic stress disorderMay be a prelude to hallucination.HallucinationRarely can be a normal phenomena:o Hypnogogic (while falling asleep)o Hypnopompic (waking from sleep)Mostly, it is a clear indication of abnormality and refers to a psychotic state unless proved otherwise.The type of hallucination, its content and other characteristic serve to differentiate psychiatric syndromes.Visual Hallucinations.Suggests organic pathology.Seen in:o Deliriumo Fronto-temporai dementiao Diffuse Lewy body disease (DLB)o Schizophrenia:Auditory Hallucinations ( AH)Most common typeSeen ino Deliriumo Dementiao Substance-induced psychosiso Schizophreniao Acute and transient psychotic disorder (ATPD)o Psychosis NOSo Maniao DepressionThird person AH, commanding AH, commentary AH- Schneider's first rank symptoms S/O Schizophrenia.Gustatoryo Dementia o Brain tumorso Schizophreniao DepressionOlfactory Hallucinationso Dementiao Frontal lobe tumorso Schizophreniao DepressionTactile Hallucinationso Deliriumo Substance withdrawal states (cocaine bugs, alcohol related delirium tremens)o Schizophrenia.Also Note:Pseudo-HallucinationThis term is used in two scenarios:o When the person says the stimulus is in his inner spac&'mind.o When he has insight (says he is abnormal and its only he is able to perceive not others- a situation occurs rarely!}.If the question included clauses such as "sees in his mental space or Tie appreciates that others can't see what he sees'.It occurs as a prelude of hallucination, when psychosis subsides (with treatment) and in some cases of dissociative disorders.DelusionIt is a problem of thought (cognition).It is a false belief.