The document provides an overview of disorders of perception including perception, imagery, synesthesia, abnormal perceptions, sensory distortions, and sensory deceptions such as illusions and hallucinations. It defines these terms and describes their characteristics. For example, it states that perception is an active process influenced by various factors, while imagery involves internal mental representations. It also distinguishes between different types of sensory distortions, illusions, hallucinations and pseudohallucinations. The document serves to explain these concepts of abnormal perception to healthcare providers.

1. Disorders of Perception
Presenter: Dr. Subodh Kumar Sharma
Resident, MD Psychiatry
Moderator: Dr. Shuva Shrestha, MD
Department of Psychiatry
NMCTH, Birgunj, Nepal

2. Contents
Perception
Imagery
Synesthesia
Abnormal Perceptions
Sensory Distortions
Sensory Deceptions
Illusion
Hallucination
Pseudo hallucination

3. Perception
 The transformation of raw sensory stimuli into sensory information that is then
decoded into meaningful perception at the cortical level involves active processes
that are influenced by attention, affect, cultural expectations, context, prior
experiences, memory and, most importantly, prior concepts.
 ‘we are not given the world: we make our world through incessant experience,
categorization, memory, reconnection’ (Sachs 1995)
 It is therefore perception is not a passive process but an active one that involves the
construction of an external world that depends on internal templates.
(SIMS’ Symptoms in Mind 5th edition)

4. Characteristics of Perception
 Are of concrete reality
 Occur in external objective space
 Clearly delineated
 Sensory elements are full and fresh
 Constant and remain unaltered
 Independent of our will
(Jaspers, 1962)

5. IMAGERY
visually descriptive or figurative language,

6. Imagery
Imagery is the internal mental representation of the world
and is actively drawn from memory.
 In day-to-day life, it is common to refer to ‘seeing in the
mind’s eyes’ or ‘hearing in the mind’s ears’.

7. Characteristics Of Imagery
Images are figurative and have a character of subjectivity
They appear in inner subjective space
They are not clearly delineated and come before us incomplete
Although sensory elements are individually the equal of those
in perception, mostly they are insufficient
Images dissipate and always have to be recreated
Images are actively created and are dependent on our will.
Jaspers (1962), SIMS’ 5th Edition

8. Applied aspect of Imagery
 Vivid sensory description to create mental pictures.
The sun was shining
brightly in the sky.
The bright yellow sun
beamed down my
shoulders, wrapping me
in a blanket of sunshine.
 In Psychopathology: understanding of the nature of imagery is
required for examining the nature of perceptions, hallucinations and
pseudohallucinations.

10. Synesthesia
 Perception of an object, presented in one sensory modality at the
same time as in different sensory modality.
“I don’t know what the color green looks like. But I know what green tastes
like!” –Taria Camerino
One of the things I love about my husband are the colors of his voice and his
laugh. It’s a wonderful golden brown, like crisp, buttery toast, which sounds
very odd, I know, but it is very real. (Cytowic and Eagleman, 2009)

11. Synesthesia continued..
Various forms:
grapheme to color; time unit to color; musical sounds to color;
general sounds to color; and, phoneme to color.
sounds to taste, sound to touch;
vision to taste
 spatially extended, but different from seeing or imagining
 Experience close to the body and within ‘peri-personal space’
 Consistent over time
 Elementary and specific in nature

12. Abnormal Perception
Sensory
Distortion Sensory
Deception
Real perceptual object
which is perceived in a
distorted way
New perception that may occur
that may or may not be in
response to external stimuli

13. Sensory Distortion
 Distortion: The act of twisting or altering something out of its true, natural, or
original state. (Merriam Websters Dictionary)
 Sensory Distortion: Real perceptual object which is perceived in a distorted
way.

14. Sensory Distortion
Intensity
Quality
Spatial form

15. Distortion in Intensity
 Hyperesthesia
 Hyperacusis
 Causes:
 Lowering of physiological
threshold.
 Intense emotions
 Experienced in:
anxiety
depressive disorder,
Hangover from alcohol
Migraine
hypochondriacal
personalities
 Hypoesthesia
Hypoacusis
 Causes:
 Increase of physiological
threshold.
 Decreased attention
 Experienced in
Delirium
 Depression
 Attention deficit disorder

17. Quality Distortion
 Drug toxicity
 Digitalis, Santonin: Xanthopsia
 Mesacline: Chloropsia
 Viagra: Erythropsia
 Lithium: Metallic taste
 Derealization
 Everything looks unreal and strange
 Mania
 Objects looks perfect and beautiful

18. Distortions in Spatial Form
 Refers to Change in perceived shape of an object
 Also known as “Dysmegalopsia”
Alice In Wonderland Syndrome (Todds’ Syndrome)

19. Distortions in Spatial Form
 Micropsia
 Seeing objects smaller than they really are or farther away than
they really are
 Retinal disease and scarring
 Accomodation and convergence disorder
 Parietal and temporal lobe disorder
 Papilledema
 Schizophrenia
 Macropsia
 Seeing objects larger than they really are
 Complete paralysis of accommodation
 Atropine/hyoscine poisoning
 Hypoxia
 Chronic arachidonitis
 Temporal lobe epilepsy

20. Lilliputian Hallucination and Micropsia

21. Distortions in Spatial Form
 Teleopsia: Object appearing far
away than it should.
 Pelopsia: Object appearing
nearer than it should
can be caused by changes in
atmospheric clarity
 sometimes by wearing a corrective
lens
 Porropsia: Experience of retreat of
subjects into the distance without
any change in space

23. Sensory Deception
 DECEPTION: the act of causing someone to accept as true or valid
what is false or invalid. (Merriam-websters dictionary)
 SENSORY DECEPTION
 Occurring of new perception that may or may not be in response to
external stimulus. (Fish’s Clinical Psychopathology, 3rd Edition)
 Altered perception of real objects to consider the perception of
objects that are not there and are new perception
(Sims’ symptoms in the mind, 5th edition)

24. SENSORY DECEPTION
ILLUSION
PSEUDO-
HALLUCINATION
HALLUCINATION

25. Illusion
Latin /illusio/ which means to mock (fake).
Stimuli from a
perceived object
Mental Image
Illusion
False Perception

26. Bunny or Bird??

27. Illusion
Not indicative of Psychopathology by themselves
Examples:
Muller-Lyer illusion
Person in dark road can mistake a shadow as attacker
May occur in any sensory modality
Delirium
Anxious and bewildered individuals
Schizophrenia
Psychomimetic drugs

28. Illusion
Completion Illusion Pareidolia
Affect Illusion
Result of inattention, misreading Result of Mood state D/t excessive fantasy thinking
and vivid visual imagery

29. Fantastic Illusion
 Fantastic illusions in which patients saw
extraordinary modifications to their
environment
 Most of the time attributed to exaggeration
and confabulation.
 More common in world of fiction than
psychiatric realm. (Hamilton 1974)

30. Illusion Vs Functional Hallucination
 Functional hallucination, which occurs when a certain percept is necessary for the
production of a hallucination, but the hallucination is not a transformation of that
perception.

31. Illusion VS Perceptual Misinterpretation
 Making a mistake as to the nature of perception without that perception being
particularly influenced by emotion mixed with fantasy.
 Rather it can be affected by previous information.

32. Hallucination
 Latin word /allucinari/
Meaning wander in mind and intent to mislead
 In English: Sir Thomas Browne (1646)
 In psychiatry: Esquirol (1817)
A perception without object

33. Hallucination
 Definition: Hallucinations proper are false perceptions that are not in any way
distortions of real perceptions but spring up on their own as something quite new and
occur simultaneously with and alongside real perception
(Jaspers 1962)

34. Definitions
 Horowitz (1975) Hallucinations are mental images that
 occur in the form of images,
 are derived from internal sources of information,
 are appraised incorrectly as if from external sources of information,
 usually occur intrusively.
 False sensory perceptions occurring in the absence of any relevant external
stimulation of the sensory modality involved.
(Kaplan & Saddock's Synopsis Of Psychiatry)

35. Causes of Hallucinations
Intense emotions
Suggestion
Disorders of sense organs
Sensory deprivation
Disorders of CNS
Psychiatric disorders

36. Pseudohallucination
 Pseudohallucination is a perceptual experience which is figurative , not
concretely real, and occurs in inner subjective space, not in external
objective space. (SIMS Symptoms In The Mind3rd Edition)
 Subjective perceptions similar to hallucinations, with respect to its
character and vividness, but that differ from those because these do not
have objective reality.
-Victor Kandinsky
 Corelates to Imagery as hallucination relates to Perception.

37. Qualities of Pseudohallucination
 Full consciousness
 Inner subjective space
 Definite outlines
 Constancy retained, insight preserved
 Relevant to emotions, needs and actions
 Depends on the observer for existence
By Jasper 1962

38. Pseudohallucination and Psychiatry
 Its presence merely doesn’t determine presence of any psychopathology.
 But, can be experienced in:
Obsessional
Depressive
Histrionic
Delirious
Psychomimmetic Drug Users

39. Hallucination and Pseudohallucination
Character Hallucination Pseudohallucination
Experience Concrete, tangible, objective , real “Inner eye” ,pictorial, subjective
Location Outer objective space Inner subjective space
Definition Definite outlines, complete sounds
Vividness Full, fresh, bright
Constancy Retained
Independence from violation Cannot be dismissed, recalled or
changed at will
Insight No distinction made from real
perception
Distinction could be made, has
quality of idea
Behavioural relevance Relevant to emotions, needs,
actions
Sensory modality Could experience in another
modality
Couldn’t experience in another
modality
Existence Exists independent of observer Dependent on observer
Attribution to abnormal state by
subject
Independent Dependent

40.  The significance of hallucination is that it almost always denotes a
morbid mental state. The significance of Pseudohallucination is in
its differential diagnosis from hallucination, as Pseudohallucination
is not necessarily psychopathological.
SIMS’ Symptoms in the Mind, 5th Edition

41. References
 Fish’s Clinical Psychopatholgy, 3rd Edition,
Patricia Casey, Berndan Kelly
 SIMS’ Symptoms in the Mind, 5th Edition,
Femi Oyebode
 Kaplan And Sadock’s Synopsis of Psychiatry, 11th edition
BJ Sadock, VA Sadock, Pedro Ruiz

42. THANK YOU!