This document discusses various types of abnormal perceptions, including sensory distortions, deceptions, illusions, pseudohallucinations, and hallucinations. It defines each term and provides examples. Sensory distortions refer to real perceptions that are perceived in a distorted way, such as increased or decreased intensity. Sensory deceptions are new perceptions that may or may not be in response to stimuli, and include illusions which involve a misperception of a real stimulus, pseudohallucinations which are vivid but non-concrete perceptions, and hallucinations which are perceptions without an external stimulus. The document outlines characteristics of each type of abnormal perception and associated psychopathologies.

1. Disorders of Perception
Dr. Ruchi Mittal
Resident,
Department of Psychiatry
NMCTH-Birgunj

2. Contents
Perception
Imagery
Synesthesia
Abnormal Perceptions
Sensory Distortions
Sensory Deceptions
Illusion
Pseudohallucination
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 the case that perception that is not a
passive process but an active one that involves
the construction of an external world that
depends on internal templates.

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 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’.
Imagery

7. • Images are figurative and have a character of subjectivity
• They appear in the inner subjective space
• They are not clearly delineated and come before us incomplete
• Although sensory elements are individually 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.
Characteristics Of Imagery

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

9. Normal Perception Imagery
Stimulus present Stimulus absent
External and objective space Internal and subjective space
Clearly delineated Incomplete and poorly delineated
Sensory elements are full and fresh Sensory elements incomplete
constant Not constant have to be recreated
Independent of will Dependent on the will

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

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. One of the things I love about my husband are the colours 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)

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

14. • Distortion: The act of twisting or altering something out of
its true, natural, or original state..
• Sensory Distortion: Real perceptual object which is
perceived in a distorted way.
• Disturbance of the mental state, with or without organic
brain pathology, may cause sensory distortion.
Sensory Distortion

15. Sensory
Distortion
Intensity Quality
Spatial
form
Experience
of time

16. Distortion in Intensity
• Hyperesthesia (increased intensity of
sensations)
• Hyperacusis
• Causes:
• Lowering of physiological
threshold.
• Intense emotions
• Experienced in:
• Anxiety
• Depressive disorder,
• Hangover from alcohol
• Migraine
• Hypochondriacal personalities

17. • Hypoesthesia (decreased intensity of
stimulus)
• Hypoacusis
• Causes:
• Increase of physiological
threshold.
• Decreased attention
• Experienced in
• Ageing
• Delirium
• Depression (lowered visual n
gustatory sensations)
• Attention deficit disorder

18.  Quality Distortion
 It is mainly visual perceptions brought about
by toxic substances.
 Drug toxicity
 Digitalis, Santonin: Xanthopsia
 Mesacline: Chloropsia
 Viagra: Erythropsia
 Lithium: Metallic taste
 Derealization
 Everything looks unreal and
strange
 Mania
 Objects looks perfect and
beautiful

19. •Distortions in Spatial Form
• Refers to Change in the perceived shape
of an object
• Also known as “Dysmegalopsia”
• Alice In Wonderland Syndrome
(Todd’s Syndrome)

20.  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 or Megalopsia
 Seeing objects larger than they really are
 Complete paralysis of accommodation
 Atropine/hyoscine poisoning
 Hypoxia
 Chronic arachidonitis
 Temporal lobe epilepsy

21.  Lilliputian Hallucination
 Alcohol Withdrawal
syndrome, Delirium,
senile psychosis

22.  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 size

23. Disorders of Experience of Time
Varieties of time:
Physical (Actual time)
Personal (Determined by
personal judgment of
passage of time)
Affected by psychiatric
disorders

24.  Sensory Deception
 DECEPTION: the act of causing someone to accept as true or valid what is
false or invalid.
 SENSORY DECEPTION
 Occurring of new perception that may or may not be in response to external
stimulus.
 Altered perception of real objects to consider the perception of objects that
are not there and are new perceptions that include:-

25. SENSORY
DECEPTION
ILLUSION
PSEUDO-
HALLUCINATION
HALLUCINATION

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

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 but visual modality is more
common
 Delirium
 Anxious and bewildered individuals
 Schizophrenia
 Psychomimetic drugs

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

31.  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 the world of fiction than
in the psychiatric realm. (Hamilton 1974)

32.  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.

33. 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.

34.  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

35. Pseudohallucination
 Pseudohallucination is a perceptual experience that is figurative, not
concretely real, and occurs in inner subjective space, not in external objective
space.
 Subjective perceptions similar to hallucinations, with respect to their 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.

36.  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

37. • Its presence merely doesn’t determine the presence of any
psychopathology.
• But, can be experienced in:
• Obsessional
• Depressive
• Histrionic Personality
• Delirious
• Psychotomimetic Drug Users
Pseudohallucination and Psychiatry

38. 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.

39.  References
 Fish’s Clinical Psychopathology, 4th Edition, Patricia Casey, Brendan Kelly
 SIMS’ Symptoms in the Mind, 6th Edition, Femi Oyebode

40. THANK YOU!