PERCEPTION

Moderator
Dr. Deoshree Akhouri
Assistant Professor
Presented By
Maria Madiha

 Individuals are capable of receiving information and
organizing it into meaningful entities. This processing
of the information to represent reality is called
PERCEPTION.
 Perception is derived from Latin term, perceptio,
which means organization, identification, and
interpretation of sensory information.
 It refers to the way world looks, sounds, feels, tastes
and smells, i.e. whatever is experienced by the person.

 Sensory Distortions:-
perception of the
constant real object in a
distorted manner.
 Sensory Deceptions:-
new perception in
response to external
stimuli.

 Sensory Distortion:-
 Change in intensity
 Change in quality
 Change in spatial form
 Distortions of experience of time

 Changes in Intensity (hyperaesthesia and hypoaesthesia):-
 Hyperaesthesia:- increased intensity of sensations.
- intense emotions
- lowering of physiological threshold
 Anxiety and depressive disorder as well as hangover from
headache or migraine,- increased sensitivity to noise
(hyperacusis)
 Hypomanic under influence of LSD (lysergic acid
diethylamide), seeing colours as bright and intense.
 A true hypoacusis occurs in delirium, threshold for all
sensations are raised, associated with depression and ADD
(attention-deficit disorder).

 Changes in Quality:- are mainly visual distortions
which colour all perceptions, because of toxic
substances.
 Xanthopsia- colouring of yellow; by santonin
 Chloropsia- colouring of green
 Erythropsia- colouring of red
 In derealisation, everything appears to unreal, while in
mania object looks perfect and beautiful.

 Changes in Spatial Form (dysmegalopsia):- is
change in perceived shape of object, caused due to-
- retinal disease
- disorders of accommodation
- disorders of convergence
- temporal lobe lesions (mainly affecting posterior lobe)
- Micropsia, seeing objects as smaller; macropsia
(meagalopsia) seeing objects as bigger.
- Macropsia and micropsia have been used for changes
in perception of size in dreams and hallucination.

 Micropsia:- is a visual disorder
in which patient sees object;
- smaller than they really are
- farther away than they really
are
- experience of retreat of objects
into distance, without any
change in size (porropsia)
 Oedema of retina image falls on
functionally smaller part of
retina
 Partial paralysis of
accommodation

 Macropsia:-
 Scarring of retina with retraction
(distortion produced by scarring is
usually irregular, metamorphopsia is
more likely to occur)
 Complete paralysis or over-reactivity of
accommodation during near vision
causes macropsia.
 If accommodation is normal but
convergence is weakened, macropsia
occurs and vice versa.
 Although hypoxia and rapid acceleration
of body can affect accommodation and
convergence, dysmegalopsia is rare
among high altitude pilots.

 Disorders of Experience of Time:- There are two
varieties of time, physical and personal.
 The psychiatric disorders are affected by personal
time.
 Time flies when one is happy (in case of mania) and
time stops when one is sad (in case of depression).
 For schizophrenics, time moves in fits and may have
delusional elaboration that clocks are being interfered
with.
 In acute organic states, personal time shows temporal
disorientation and overestimation of time in milder
forms.

 Sensory Deceptions:-
Illusions- misinterpretations of stimuli
Hallucinations- perception without adequate
external stimuli

 Stimuli from perceived object is combined with
mental image to produce false perception.
 Occur in absence of psychiatric disorder, for example
person walking along dark road interprets shadow as
threatening attackers.
 Occurs in delirium when perceptual threshold is
raised.
 Fantastic Illusions- patient sees extraordinary
modifications in his/her environment.

Sims (2003) explained three types of illusions:-
 Completion Illusions:- depend on inattention such as
misreading words in newspaper.
 Affect Illusions:- arise in context of particular mood
(seeing the deceased)
 Pareidolia:- illusions occurring without any effort
from patient, may be the result of excessive fantasy
thinking and visual imagery such as vivid pictures in
the clouds.

 Intellectual Misinterpretation:- interpretation of stimuli
due to lack of appropriate knowledge.
 Functional Hallucination:- occurs in response to
environmental stimulus but both provoking stimulus and
hallucination are perceived by patient simultaneously.
 Trailing Phenomena:- Although it is not exactly illusion
but it occurs when moving objects are perceived as series
of discreet and discontinuous images.

 Means “perception without an object”; doesn’t cover
functional hallucinations.
 According to SCAN (WHO, 1998), hallucinations are
false perceptions.
 According to Jaspers; “false perception, which is not a
sensory distortion or misinterpretation, but occurs at
the same time as real perceptions”.

 According to Gruhle, schizophrenic experience is not
perceptual, but patient is compelled to formulate some
experiences in perceptual form.
 Hallucinations VS Perceptions:- Hallucinations comes
from ‘within’, although subject reacts to them as if they
were true perceptions coming from ‘without’.

 Pseudo-Hallucinations- are type of mental image
that, although clear and vivid
- lack substantiality of perceptions
- seen in full consciousness
- known to be not real perceptions
- Not located in objective space but in subjective; inside
the head.
 Pseudo-hallucinations stems from 2 different
approaches- one based on insight (Hare, 1973) and
one based on whether images lies in inner or outer
perceptual space.

Intense Emotions
Suggestion
Disorders of Sense Organs
Sensory Deprivation
Disorders of CNS

 Emotion is any conscious experience characterized by
intense mental activity and a certain degree of pleasure or
displeasure.
 In depressed patients, with delusions of guilt,
hallucinations are disjointed, saying single words or short
phrases, etc.
 Occurrence of continuous persistent hallucinatory voices
in severe depression should arouse suspicion of
schizophrenia or some inter-current physical disease.
 Hallucinations that occur in schizophrenia are often
persecutory in nature and may consist of voices giving
commentary on person’s actions.

 Experiments show that normal subjects could be
persuaded to hallucinate (visual/auditory), either by
hypnosis or by brief task-motivating instructions.
 Ganser Syndrome (psychogenic in nature), opens
possibility of role of suggestion in genesis of
hallucinations and is recognised to occur in variety of
psychiatric disorders such as schizophrenia,
dissociative disorder, etc.

 Hallucinatory voice may occur in ear diseases, visual
hallucinations in eye diseases but there is no disorder of
CNS.
 Charles Bonnet Syndrome is a condition where visual
hallucinations occur in absence of any psychopathology
and in clear consciousness.
 It is associated with central or peripheral reduction in
vision, common in old people but can also occur in young.
 Peripheral lesions of sense organs may play role in
hallucinations of organic states and has been shown that
negative scotomota are found in alcohol misuse patients.

 These hallucinations are changing visual
hallucinations and repetition of words and phrases.
 Sensory isolation produced by deafness may cause
paranoid disorders in deaf (Cooper, 1976).
 Similarly, use of protective patches (black patch
disease), after cataract surgery, may cause delirium,
along with cognitive impairments due to ageing.

Lesions of diencephalons and cortex may
produce hallucinations that are mostly visual
but could also be auditory.

 Hallucinations of individual senses includes:-
- hearing
- vision
- smell
- taste
- touch
- pain and deep sensation
- sense of presence

 Auditory hallucinations may
be
- elementary noises (bells), in
organic states and
schizophrenia
- partly organised, such as
music
- completely organised, such as
hallucinatory voices
- occurs in delirium, dementia
as well as depression

 Voices are characteristics of schizophrenia, occurring
at any stage of illness and occasionally in delirium
and dementia.
 Hallucinatory voices were once known as
‘phonemes’, given by Wernicke in 1900.
 Imperative Hallucinations:- voices giving
instructions to patient, who may/may not feel obliged
to carry out.

 Auditory hallucinations may be abusive; as a result of
which patient may attack those whom they believe to be
responsible.
 Thought Echo/Sonorisation (echo de pensee,
Gedankenlautwerden):-
- hearing one’s own thoughts being spoken aloud;
- Patients hearing voices have slight movements of tongue,
lips and laryngeal muscles.
- Patients may insist that the origin of voices are result of
witchcraft, telepathy, radio, television, etc.

 Visual hallucinations
may be:-
- Elementary vision in the
flash of light
- Partly organised; patterns
- Completely organised;
vision of people,
animals, etc.

 Scenic Hallucinations:- in which whole scenes are
hallucinated like a movie, more common in psychiatric
disorders associated with epilepsy.
 They are common in psychiatric disorders associated with
epilepsy.
 Patients with temporal-lobe epilepsy and with late onset
schizophrenia may have both visual and auditory
hallucinations.

 Lilliputian Hallucinations:- patient sees tiny people as a
result of micropsia affecting visual hallucinations,
accompanied by pleasure and amusement.
 Visual hallucinations are more common in acute organic
states with clouding of consciousness and are extremely
rare in schizophrenia.
 Occasionally, they occur in absence of psychopathology
or brain disease and Charles Bonnet syndrome must be
considered as likely differential diagnosis.

 Hallucination of odour can occur:-
- in schizophrenia and organic states
- in depressive psychosis (uncommon)
 It may be difficult to distinguish it
with delusion; since people insist that
they emit a smell.
 Episodes of temporal lobe
disturbance are often ushered in by
aura involving unpleasant odour such
as burning paint.
 Padre Pio Phenomenon:-
hallucination of pleasant smell (smell
of roses).

Hallucination of taste occurs in schizophrenia
and acute organic states
Difficult to distinguish that patient actually
tastes something odd or it is a delusional effect.
Depressed patients often describe loss of taste
or state all food tastes the same.

 Formication:- is a feeling that animals are crawling
over body, not uncommon in acute organic states.
 Cocaine Bug:- Formication occurring with delusions
of persecution in cocaine pyschosis.
 Sexual Hallucinations:- occur in acute and chronic
schizophrenics.
 Sims (2003) explained 3 types of tactile hallucination;
namely superficial, kinaesthetic and visceral.

 Superficial
Hallucinations:- affects
skin; is of 4 types
- thermic; cold wind blowing
across face
- haptic; feeling hand
brushing against skin
- hygric; feeling water
running from head to
stomach
- paraesthetic; pins and
needles

 Kinaesthetic Hallucinations:- affects muscles and
joints; feeling of limbs being twisted and occurs in
schizophrenia.
 Vestibular sensations, such as sinking in bed, is
regarded as a variant of kinaesthetic hallucinations.

 It is also known as visceral hallucinations (Sims,
2003)
 Complains of twisting and tearing pains by chronic
schizophrenics.
 Delusional Zoopathy:-
- delusional belief that animal is crawling about the
body
- patient can feel it and describe in detail
- in some cases it is associated with organic disorder.

 It is difficult to classify abnormal sense of presence,
as even normal people report the sense that someone
is present when they are alone; often complaining that
is someone behind them.
 The sense of presence can occur in healthy people as
well as in organic states, schizophrenics or in hysteria
patients.

 Also known as hallucinosis, are those disorders that
are persistent hallucinations in any sensory modality
in absence of other psychotic features.
 Alcoholic Hallucinosis:- are usually auditory, due to
misuse of alcohol and occur during periods of
abstinence, may be threatening.
 Organic Hallucinosis:- are present in patients of
dementia (20-30%), especially Alzheimer’s.
Disorientation and memory impairment are also
reported.

 Functional Hallucinations:- Auditory stimulus
causes hallucination, requiring presence of another
real sensations.
 Not uncommon in chronic schizophrenics but may be
mistaken for illusion.
 Reflex Hallucinations (synaesthesia):- experience of
a stimulus in 1 sensory field produces hallucination in
another.
 They are the morbid form of synaesthesia.

 Extracampine Hallucinations:- is a type of
hallucination that occurs outside the limits of sensory
field.
 Occur in healthy people as hypnogogic hallucinations
as well as in schizophrenia or organic conditions,
including epilepsy.

 Autoscopy (phantom mirror-
image):-
- patient sees himself and knows
that it is him
- may occur in healthy people,
emotionally upset or when
exhausted.
 Negative Autoscopy:- patient
sees in mirror and sees no
image.
 Internal Autoscopy:- patient
sees his/her internal organs.

- It is not just visual hallucinations, kinaesthetic and
somatic sensation must also be present for
hallucination
- occasionally, it is a hysterical syndrome
- schizophrenics could witness them but most common
in acute and sub-acute delirious states.
- organic states most associated are epilepsy, focal
lesions affecting parieto-occipital regions, toxic
infective states whose effect is greatest in basal
regions.

 Hypnagogic Hallucinations:-
- occurs when subject is falling asleep or is drowsy
- are discontinuous
- appears forceful on subjects
- not part of experience of subject
- auditory hallucinations are common
- EEG shows loss of alpha rhythm at the time of
hallucination
 Hypnopompic Hallucinations:-
- occurs when subject is awake
- hallucinations persisting from sleep even when eyes are
open

 Organic Hallucinations:-
- can occur in any sensory modality
- occur in variety of neurological and psychiatric disorders
 Organic visual hallucinations includes:-
- Eye disorders
- Charles Bonnet Syndrome
- Dementia as well as delirium and substance abuse
 Organic somatic hallucination includes phantom
limbs; not receiving any sensations from a limb, either
due to amputation or damage to sensory pathways

 Body Image Distortions:-
 Perceived magnification of body parts
(hyperschemazia), occurs in organic, non-organic
and psychiatric conditions; such as Brown- Sequard
paralysis, multiple sclerosis, hypochondriasis,
depersonalization, etc.
 Perception of body part as absent (aschemazia) or
diminished (hyposchemazia), occurs in parietal lobe
regions.

 Koro:- belief that penis is shrinking and will retract
into abdomen; caused death in South-East Asia.
 Distortion of body (paraschemazia) is a feeling that
body part is distorted, twisted or separated from rest
of the body; occurring with hallucinogenic use, with
epileptic aura and migraine too.
 Hemisomatognosia is unilateral lack of body image,
patient behaves as if one side of the body is missing;
occurring with epileptic aura.

 Anosognosia is denial of illness.
 Somatoparaphrenia is delusional beliefs about body.
 Gerstman syndrome consists of agraphia, acalculia,
finger agnosia and right/left distortion.

 In organic hallucinations, the patient is usually terrified by
the visual hallucinations and may even try desperately to
get away from them.
 The combination of the persecuted attitude and the visual
hallucinations leads to resistance to all nursing care &
impulsive attempts to escape from the threatening
situation, the exception is Lilliputian hallucinations.

 Patients with depression often hear disjointed voices
abusing them or telling them to kill themselves.
 In Schizophrenia, the onset of voices is often very
frightening and the patient at times may attack the person
he believes to be the source.
 Those with chronic schizophrenia on the other hand are
often not troubled by the voices and may treat them as old
friends, but a few patients complain bitterly about them.

 Perception is the way individual perceives the stimuli,
interprets it and organises it into meaningful
something.
 Perceptual distortion is perceiving the stimuli in
distorted form; sensory deception and distortion.
 Sensory distortions include change in intensity,
quality, spatial form and experience of time.
 Sensory deceptions include illusions and
hallucinations.
 Illusions are misinterpretation of stimuli.
 Hallucinations are false perception.

 Pseudo-hallucinations are involuntary sensory experiences
vivid enough to be regarded as a hallucination, but
recognised by the patient not to be the result of external
stimuli.
 Various causes of hallucinations have been recognised;
emotions, suggestion, disorder of sense organs, sensory
deprivation and disorders of CNS.
 There are various types of hallucinations; namely,
auditory, visual, tactile, olfactory, gustatory, visceral, etc.
 Some especial types of hallucinations are also witnessed;
functional, reflex, extracampine, autoscopy, hypnogogic
and hypnopompic.

 Introduction to Psychology, Morgan and King
 Fish’s Clinical Psychopathology
 Sim’s Symptoms in The Mind
 Synopsis of Psychiatry, Kaplan and Sadock

PERCEPTION

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