Dr Deepthi V H

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.

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.

Changes in spatial form

Metamorphopsia

Alteration in the customary shape of perceived object.

Dysmegalopsia

Retinal disease,disorders of accomodation and convergence,temporal & parietal lobe lesions

Rare association with schizophrenia.

May occur in poisoning with atropine or hyoscine.

Macropsia : size of perception is large.

Micropsia : size of perception is small.

Hemimicropsia : apparent reduction in one hemi field of vision – temporal lobe epilepsy

Palinopsia : 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 colour

Acrometopsia :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 quality

Colouring 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.

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

Rare phenomenon

Described sometimes with organic states & also with schizophrenia

Eg: a patient watching television experienced a feeling of competition between the visual and auditory perceptions

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

Illusions : Misinterpretations of stimuli arising from an external object

Hallucinations :Perception without an adequate external stimulus.

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.

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 interoceptivepercept that does not correspond to an actual object (smythies ,1956).

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 organs

Sensory deprivation

Disorders of central nervous system.

Auditory hallucinations

elementary & unformed- bells, whistling, machinery or rattles.

Completely organized as hallucinatory voices schizophrenia

May also occur in chronic alcoholic hallucinosis or affective psychosis occasionally

Visual hallucination

Elementary- in the form of flashes of light

Partly organized- patterns

Completely organized-visions of people, objects or animals

Occipital lobe tumours

Post-concussional state

Metabolic disturbances-hepatic failure

Alzheimer’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 elderly

Associated with central & peripheral reduction in vision

Importance in differential diagnosis.

Delirium tremens

Alcohol 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’)

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

Schizophrenia

Withdrawal 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)

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