Dr Deepthi V H

Disorders of perception

Sensation : is the first stage in receiving information from outside the self.

Perception : occurs when a stimulus has undergone processing according to its form, color, motion.

The subject is able to recognize that an object is in his field of vision- sensation intact

He is unable to recognize what the object or its function is - impaired perception

Constant real perceptual object in a distorted way…………sensory distortion.

New perception that may or may not be in response to an external stimulus………..sensory deception.

Sensory distortions….a) Visual perception b) Auditory perception

c) Splitting of perception

Sensory deceptions …a) Illusions b) Hallucinations c) Pseudohallucinations.

Disorders of perception

Disturbance of the mental state with/without organic brain pathology

Involve any elementary aspects of perception like uniqueness , size , shape, colour ,location,motion or general quality.

Significance ,,,,? Perceived object is correctly

recognized and identified yet there is a deviation from its customary appearance.

Sensory distortions

Changes in spatial form Metamorphopsia Alteration in the customary shape of perceived object.DysmegalopsiaRetinal disease,disorders of accomodation and

convergence,temporal & parietal lobe lesionsRare association with schizophrenia.May occur in poisoning with atropine or hyoscine.

Elementary aspects of visual perception

Macropsia : size of perception is large.Micropsia : size of perception is small.Hemimicropsia : apparent reduction in one hemi field

of vision – temporal lobe epilepsyPalinopsia : recurrence or prolongation of visual

phenomenon beyond the customary limits of appearance of the real event

eg: “cat noticed in the street one day kept appearing at various times and situation over the next few days”

Paraprosopia :when metamorphopsia affect faces.

Changes in intensity Visual hyperasthesia: increased intensity of colourAcrometopsia :complete absence of colour -unilateral/bilateral occipital lesions (lingual,

fusiform gyri)Dyschromatopsia : perversion of colour perception -unilateral posterior lesions

Spatial location Telopsia : subjects appearing far away Pelopsia : subjects appearing nearer. Alloaesthesia :when the perceived object is in a

different position Akinetopsia: unable to perceive the motion of the

object. seen in B/L posterior cortical damage.Eg: ‘ she had difficulty in pouring tea into a cup because

the fluid appeared to be frozen’.

Changes in qualityColouring of yellow- xanthopsia,green-chloropsia &

red- erythropsia. -poisoning with digitalis

Derealization : everything appears unreal and strange. Eg: a factory worker sees a grass hopper and becomes

disturbed and excited at the site of this very strange and unknown animal.

Uniqueness of perception Palinacousis : persistance of sounds that are heard Intensity of perception Hyperacusis : increased sensitivity to noise. Anxiety & depressive disorders, migraine,

hangover from alcohol. Hypoacusis: threshold for noise is raised Delirium, depression & attention-deficit

disorder.

Elementary aspects of auditory perception

Unable to form the usual, assumed links between two or more perceptions.

Rare phenomenonDescribed sometimes with organic states & also with

schizophrenia Eg: a patient watching television experienced a

feeling of competition between the visual and auditory perceptions

Splitting of perception

Physical and personal

Personal: Determined by personal judgement of passage of time.

Influence of mood: happy-time flies, sad-slow Affected by psychiatric disorder Severe depression- time passes slowly Mania- time speeds by

Distortions of the experience of time

Illusions : Misinterpretations of stimuli arising from an external object

Hallucinations :Perception without an adequate external stimulus.

Sensory deceptions

Completion illusions: depends on inattention for their occurrence.

‘ _ook’ misread as ‘Book’ though the faded letter was ‘L’Affect illusions: arise in context of particular mood

state. Delirious person may perceive the innocent gestures as

threatening. Pareidolia: vivid illusions without patients effort.Subject sees vivid pictures in fire or in clouds without

any conscious effort.

Illusions

A perception without an object (Esquirol 1817).

A false perception which is not a sensory distortion or a misinterpretation ,but which occurs at the same time as real perceptions(Jaspers ,1962).

A hallucination is an exteroceptive or interoceptive percept that does not correspond to an actual object (smythies ,1956).

Hallucinations

A hallucination is a perception without an object or the appearance of an individual thing in the world without any corresponding material event (cutting 1997).

According to Slade (1976) ,3 criteria are essential (a) percept like experience in the absence of external stimuli, (b) percept like experience that has the full force and impact of a real perception (c ) percept like experience that is unwilled ,occurs spontaneously and cannot be readily controlled by the percipient.

Intense emotions.Disorders of sense organsSensory deprivationDisorders of central nervous system.

Causes of hallucinations

Auditory hallucinationselementary & unformed- bells, whistling, machinery or

rattles. Completely organized as hallucinatory voices

schizophrenia May also occur in chronic alcoholic hallucinosis or

affective psychosis occasionally

Hallucinations of individual senses

Visual hallucination Elementary- in the form of flashes of light Partly organized- patterns Completely organized-visions of people, objects or

animalsOccipital lobe tumoursPost-concussional stateMetabolic disturbances-hepatic failureAlzheimer’s disease, senile dementia

Charles Bonnet’s syndrome( phantom images)- Individuals experience complex visual hallucinations

in association with impaired vision without any psychopathology or disturbance of consciousness

More common in elderlyAssociated with central & peripheral reduction in

vision Importance in differential diagnosis.

Delirium tremensAlcohol withdrawal syndrome characterized by gross

changes in perception, mood and conscious state.Pareidolic or affective illusions are often prodromal.Lilliputian hallucinations-seeing tiny people or objects. accompanied by pleasure & amusement.

Superficial : Affecting skin sensation

Thermic - heat and cold (‘my feet on fire’)Haptic - of touch (‘a dead hand touched me’)Hygric – a perception of fluid (‘ I can feel a water level

in my chest’)

Hallucinations of bodily sensation

Kinaesthetic hallucinations : The patient feels that his limbs are being bent or twisted or his muscles squeezed.

SchizophreniaWithdrawal state from benzodiazepine or alcohol

intoxication. Eg: ‘I thought my life was outside my feet and made

them vibrate’

Olfactory hallucination: schizophrenia , epilepsy.

Hallucination of smell which may or may not be unpleasant.

Eg : people are pumping anaesthetic gas into the house which the patient alone can smell.

Gustatory hallucinations: schizophrenia, depression, temporal lobe epilepsy, psychotropic drugs- lithium or disulfiram.

Eg: In schizophrenia and depression the flavour of food may disappear alltogether or become unpleasant.

Autoscopy (phantom mirror image) : subjects see an image of themselves in external space viewed from within their own physical body.

Negative autoscopy : for instance, the patient looks in the mirror and sees no image at all.

Extracampine hallucination (concrete awareness): experienced outside the limits of the sensory field, outside the visual field or beyond the range of audibility

Eg:‘ I keep on hearing them talking about my disease down in the post office’ (half a mile away)

Other abnormalities of perception

Hypnogogic hallucination: perceptions that occur while going to sleep.

Hypnopompic hallucination: perceptions that occur on waking.

May be visual, auditory or tactile Occur in many people in good health Described with narcolepsy, cataplexy and sleep

paralysis. Toxic states- glue sniffing , acute fever , post infective

depressive states.

Eg - ‘a feeling of someone pushing him over the bed’ or ‘seeing a man coming across the bedroom’

Functional hallucination : External stimulus is necessary to provoke hallucination but the stimulus is experienced as well as the hallucination

Eg : ‘ A schizophrenic patient heard hallucinatory voices only when water was running through the pipes’.

Reflex hallucination : A stimulus in one sensory modality producing a hallucination in another.

Eg : ‘ I can feel you writing in my stomach’

SIMS’ Symptoms in the mind psychopathology, fourth edition.

Fish’s clinical psychopathology, third edition.

Thank you