DISORDERS OF PERCEPTION
Perception - (from the Latin perceptio, percipio) is
the organization, identification, and interpretation
of sensory information in order to represent and
understand the environment

Abnormal
perception
Sensory
deceptions
Sensory
distortions

TYPES
 Sensory Distortion - real perceptual object
which is perceived in a distorted way
 Sensory Deception - new perception that
may occur that may or may not be in
response to external stimuli
 Disorders in the experience of time

Sensory Distortion
Changes in perception that are the result of :
1. Change in the intensity
2. Quality of the stimulus
3. Spatial form of the perception
4. Distortions of the experience of time
5. Splitting of perception

Changes in Intensity
• Increased intensity of sensation - Hyperesthesia seen in
increasing sensations or lowering of physiological threshold.
• Seen in:
 anxiety
 depressive disorder,
 Hangover from alcohol
 Migraine
 Hypochondria
 Increased sensitivity to noise – Hyperacusis is associated with
Anxiety and depressive disorders as well as hangover from
alcohol and migraine.
 Decreased sensitivity to noise – Hypoacusis, occurs in
delirium, where the threshold for all sensations is raised.
Hypoacusis feature of other disorders associated with
attentional deficits such as depression and attention- deficit
disorder

Hyperaesthesia

Changes in quality
Visual perception
• Xanthopsia- Coloring of yellow
• Chloropsia - Coloring of green
• Erythropsia- Coloring of red
•which is result of drugs (poisoning with
mescaline or digitalis)

Complete absence of color

Changes in spatial form
• Change in percieved shape of an object, can
result from
 Retinal disease
 Disorders of accommodation
 Temporal and Parietal Lobe Lesions
 Poisoning with Atropine and Hyoscine
 Schizophrenia

 Micropsia - a visual disorder in which the patient
sees objects
Smaller than they really are
Farther away than they really are
 Macropsia or Megalopsia - opposite to
micropsia
 Porropsia : Experience of retreat of subjects into
the distance without any change in space
 Dysmegalopsia: Objects are perceived larger in
one side and smaller in the other.
Metamorphosia: Irregular in shape.

 Micropsia - a visual disorder in which the
patient sees objects
Smaller than they really are
Farther away than they really are
 Macropsia or Megalopsia - opposite to
micropsia
 Porropsia : Experience of retreat of subjects
into the distance without any change in space
 Dysmegalopsia: Objects are perceived larger
in one side and smaller in the other.
Metamorphosia: Irregular in shape

Teleopsia
Object appearing far
away
Pelopsia
Object appearing nearer
than it should

Distortions in the experience of time
• Mania- Time passes quickly
• Depression- Time passes slowly
• Temporal lobe lesions- feels time either passes
slowly or quickly
• Schizophrenia- have abnormalities of time
judgment, estimating intervals to be less than
they are

Splitting of perception
Seen sometimes with organic states and with
schizophrenia
Unable to form usual assumed link between
two or more perceptions
While watching TV experiencing a feeling of
competition between the visual and auditory
perception and not coming out of the same
source

Illusion
Hallucination
Misinterpre
tations of
stimuli
from
external
object
Perceptions
without
external
stimulus

Stimuli
from
perceived
object
Mental
image
False
perception

Illusions - Stimuli from a perceived object are
combined with a mental image to produce a
false perception
Types of Illusion
 Complete Illusion- These depends on misreading words in
newspapers or missing misprints because we read the word
as if it were capable
 Affect Illusion-These arise in the context of
particular mood state
 Paradolia- vivid illusions occur without the patient
making any effort ; are the result of excessive fantasy
thinking and a vivid visual imagery

Hallucination
A perception without an object
A false perception which is not a sensory
distortion or a misinterpretation but which occurs
at the same time as real perceptions
Causes:
• Intense emotions
• Suggestion
• Disorders of sense organs
• Sensory deprivation
• Disorders of CNS

Disorders of a peripheral sense organ
 Hallucinatory voices may occur in ear disease
and visual hallucinations in diseases of the eye
 Charles Bonnet syndrome (phantom visual
images) is a condition in which complex visual
hallucinations occur in the absence of any
psychopathology and in clear consciousness
 It is associated with either central or
peripheral reduction in vision

Charles Bonnet syndrome
 Features of delirium, dementia, organic affective or
delusional syndromes, psychosis, intoxication or
neurological disorders with lesion of central visual
cortex are absent
 Hallucinations are located in external space, much more
vivid than the patient’s impaired vision would otherwise
permit
 May be modifiable by voluntary control
 Usually insight is there concerning their unreality
 Can be either elementary or complex

Sensory Deprivation
 If all incoming stimuli are related to minimum in a
normal subject they will begin to hallucinate after
few hours
 Usually these are changing visual
hallucinations and repetitive phrases
 BLACK PATCH DISEASE delirium following
cataract extraction in the aged
result of sensory deprivation and mild senile
brain changes

Hallucinations and senses
Hearing
Vision
Smell
Taste
Touch
Pain and deep sensation
The sense of presence

Hearing
Hearing may be elementary or unformed
• Elementary – noises, bells or undifferentiated
whispers ; in organic states
• Partly organized- music
• Completely organized –”Voices” are
characteristic of schizophrenia (also
occurring in organic states: delirium,
dementia and sometimes in severe
depression or mania)

Hearing
Auditory hallucinations
Adverse
Neutral
Helpful
Incomprehensible nonsense
Thought echo - hearing one’s own thoughts being
spoken loud, voice may come from inside or
outside the head
GEDANKENAUTWERDEN - thoughts are spoken at the
same time or before they are occurring
ECHO DE LA PENSES - thoughts are spoken just after they
occurred

Hearing
Imperative/Command hallucination:
• Voices sometimes act upon individuals and
give instructions.
• may or may not act upon them
• Voices speak about the person in the third person
and may give a running commentary on their
actions, although this was one thought to be
diagnostic of schizophrenia, this is no longer the
case since these symptoms have also been
described in mania
• This kind of hallucinations are usually
abusive

Vision
• Elementary- flashes of light
• Partly organized- patterns
• Completely organized- visions of people animals
or objects
• Scenic hallucinations- whole scenes
are hallucinated like a cinema film
More commonly seen in delirium
Also seen in psychiatric disorders associated with
epilepsy

Vision
• Visual hallucinations are more common in
acute organic states with clouding of
consciousness than in functional psychosis
• Patients with temporal-lobe epilepsy may
have combined auditory and visual
hallucinations
• Some patients with schizophrenia may see
and hear people being tortured, murdered and
mutilated

Smell (olfactory)
Seen in
• Schizophrenia
• Organic states like temporal lobe epilepsy are
often ushered in by an aura involving an
unpleasant odour such as burning paint or
rubber with or without fit
• Depression (uncommon)
• PADRE PIO PHENOMENON- religious
people can smell roses around certain saints

Taste (gustatory)
• Seen in
• Schizophrenia
• Organic states
• Depressed patient often describes loss of taste

Touch (Tactile)
• Formication- a feeling that animals are
crawling over the body (organic states)
• Cocaine bug – formication occurring with
delusion of persecution in cocaine psychosis
• Sexual Hallucinations- seen in acute and
chronic schizophrenia
• Types of tactile hallucination
1. Superficial,
2. Kinaesthetic,
3. Visceral

Superficial
 Thermic (cold wind blowing across the face)
 Haptic (feeling a hand brushing against the skin)
 Hygric (feeling fluid )
 Paraesthetic (feeling pins and needles)
Kinaesthetic
 Affects muscles and joints
 Patient feels their limbs are being twisted pulled
or moved
 Seen in schizophrenics
 Organic states such as alcohol intoxication and
benzodiazepine withdrawal

Pain and deep sensation
• Visceral hallucinations
• Twisting and tearing pains
• Very bizarre complaints- organs being ripped
out and flesh ripped from his body
• Seen in chronic schizophrenia
• Delusional zoopathy in which delusional
belief that there is an animal crawling about in
the body and also a hallucinatory component
since the patient feels it & can describe it

Sense of presence
• vivid sensation that somebody
(distinct from oneself) is present
nearby
• Organic states
• Schizophrenia
• Hysteria
• Normal people – Reverently religious

Special kinds of hallucination
• Reflex hallucinations
• Synaesthesia is the experience of a stimulus in
one sense modality producing a sensory
experience in another
• Can occur under the influence of
hallucinogenic drugs such as LSD or
mescaline when the subject might describe
feeling, tasting and hearing colours
simultaneously

Special kinds of hallucination
• Autoscopy is the experience in which an
individual perceives the surrounding
environment from a different perspective, from
a position outside of their own body.
• Autoscopy comes from the ancient Greek
αὐτός ("self") and σκοπός ("watcher")
 Internal Autoscopy – Experience of seeing or
vividly describing one’s internal organs
 External Autoscopy - Person sees an image of
himself outside his own body
Negative Autoscopy: patients look in the
mirror and see no image

Hypnagogic and hypnopompic
hallucinations
• Hallucinations occur when the person is
falling asleep or waking up
• Hypnagogic hallucinations is about three
times more common than hypnopompic
hallucinations.
• Hypnopompic a better indicator of narcolepsy.
• Commonest is auditory. His name being called
• May be geometrical designs , abstract shapes ,
faces, figures or scenes from nature

Phantom Limb
• Most common organic somatic hallucination.
• Patient feels that they have a limb from which
in fact they are not receiving any sensations
either because it has been amputated or
because the sensory pathways from it have
been destroyed.
• In rare cases with thalamo−parietal lesions
the patient describes a third limb

Thought disorder
A thought disorder is any disturbance in cognition that
adversely affects language and thought content, and
thereby communication
 Content-thought disorder
thought disturbance in which a person experiences
multiple, fragmented delusions, typically a feature
of schizophrenia
 Formal thought disorder
also known as disorganized speech – evident
from disorganized thinking, and is one of the
hallmark features of schizophrenia

Types
• Alogia – A poverty of speech, either in amount or content
• Blocking or thought blocking – An abrupt stop in the
middle of a train of thought
• Circumstantial speech - An inability to answer a question
without giving excessive, unnecessary detail.
• Clanging – A severe form of flight of ideas whereby ideas
are related only by similar or rhyming sounds rather than
actual meaning.
• Derailment -Thought frequently moves from one idea to
another which is obliquely related or unrelated, often
appearing in speech but also in writing
• Echolalia– Echoing of another's speech that may only be
committed once, or may be continuous in repetition
• Flight of ideas - a form of formal thought disorder marked
by abrupt leaps from one topic to another

Types
• Illogicality– Conclusions are reached that do not follow
logically
• Incoherence (word salad)– Speech that is unintelligible
because, though the individual words are real words, the
manner in which they are strung together results in incoherent
gibberish
• Neologisms – forms completely new words or phrases whose
origins and meanings are usually unrecognizable
• Perseveration– Persistent repetition of words or ideas even
when another person attempts to change the topic
• Pressured speech - Rapid speech without pauses, difficult to
interrupt.
• Self reference – Patient repeatedly and inappropriately refers
back to self
• Tangential speech – Wandering from the topic and never
returning to it or providing the information requested

Delusions
Fixed, false beliefs that conflict with reality. Despite contrary evidence, a
person can’t let go of their convictions
Delusions are categorized into four different groups:
• Bizarre delusion: Delusions which are clearly not understandable to same-
culture peers and do not derive from ordinary life experiences
Example: a belief that someone replaced all of one's internal organs with
someone else's without leaving a scar
• Non-bizarre delusion: A delusion that, though false, is at least technically
possible
Example: the affected person mistakenly believes that they are under
constant police surveillance
• Mood-congruent delusion: Any delusion with content consistent with
either a depressive or manic state
Example: a depressed person believes that news anchors on television
highly disapprove of them, or a person in a manic state might believe they are
a powerful deity
• Mood-neutral delusion: A delusion that does not relate to the sufferer's
emotional state
Example: a belief that an extra limb is growing out of the back of one's
head is neutral to either depression or mania

Themes
• Delusion of control: False belief that another person, group of
people, or external force controls one's general thoughts, feelings,
impulses, or behaviors
• Cotard delusion: False belief that one does not exist or that one
has died
• Delusional jealousy: False belief that a spouse or lover is having an
affair, with no proof to back up
• Delusion of guilt or sin (self-accusation): Ungrounded feeling of
remorse or guilt
• Delusion of mind being read: False belief that other people can
know one's thoughts
• Delusion of thought insertion: Belief that another thinks through
the mind of the person
• Delusion of reference: False belief that insignificant remarks,
events, or objects in one's environment have personal meaning or
significance. Usually the meaning assigned to these events is
negative

Themes
• Erotomania: False belief that another person is in love with them (usually
famous one)
• Religious delusion: Belief that the affected person is a god or chosen to act
as a god
• Somatic delusion: False belief is that the body is somehow diseased,
abnormal or changed.
A specific example of this delusion is delusional parasitosis: Delusion in
which one feels infested with insects, bacteria, spiders, lice, fleas, worms, or
other organisms
• Delusion of poverty: Person strongly believes they are financially
incapacitated
• Grandiose delusions: False beliefs that one is famous, omnipotent or
otherwise very powerful
• Persecutory delusions: In which the affected person wrongly believes that
they are being persecuted, spied on, attacked, poisoned or drugged
The individual thinks that the persecutors have the intention to cause harm