PERCEPTION DISORDERS
Perception:
The process of transferring physical stimulation into psychological information; mental process
by which sensory stimuli are brought to awareness.
Without perception we still be able to see, hear, test, smell and or have skin sensations, but we will not understand what we see, hear
and so on Perceptual Disorders:
Perceptual Disorders Cognitive disorders characterized by an impaired ability to perceive the
nature of objects or concepts through use of the sense organs. These include spatial neglect
syndromes, where an individual does not attend to visual, auditory, or sensory stimuli presented
from one side of the body.
Types:
Sensory Distortion
Constant 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 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 cal personalities
Increased sensitivity to noise – Hyperacusis
Decreased sensitivity to noise – Hypoacusis
Delirious
Depression
Attention deficit disorder
Change in Quality:
Visual perception – affected by this are brought about by toxic drugs
Xanthopsia- Coloring of Yellow
Chloropsia - Coloring of green
Erythropsia- Coloring of red
Derealization- Everything looks unreal and strange
Mania- looks perfect and beautiful
Changes in Spatial Form
Change in perceived shape of an object
Retinal disease
Disorders of accommodation
Temporal and Parietal Lobe Lesions
Poisoning with Atropine and Hyoscine
SCHIZOPHRENIA
Distortions In The Experience Of Time
Psychopathological point of view
Physical- Determined by physical events
Personal- Personal judgment of passage of time
i. Mania- Time passes quickly
ii. Depression- Time passes slowly
iii. Acute Schizophrenia- personal time goes in fits and starts
iv. Acute organic states (temporal disorientation) disorders of time is seen in milder form
there may be over estimation of time.
Sensory Deception:
Illusions- Misinterpretation of a single stimuli arising from a single stimuli.
Stimuli from a perceived object are combined with a mental image to produce a false
perception.
Derived from set and lack of perceptual clarity
Delirium
Severe depression with delusions of guilt
Types of Illusion:
1. Complete Illusion-These depends on misreading words in newspapers or missing
misprints because we read the word as if it were capable
2. Affect Illusion- These arise in the context of particular mood state
3. Paradolia- vivid illusions occur without the patient making any effort; are the result
of excessive fantasy thinking and a vivid visual imagery.
HALLUCINATIONS:
False perception which is not a sensory distortion or misinterpretation but which occurs
at the same time as real perception.
Essential criteria for an operational definitions:
a) Percept like experience in the absence of external stimuli
b) Percept like stimuli which has full force and impact of real perception
c) Percept like experience which is unwilled
d) occurs spontaneously and cannot be readily controlled by percipient.
Causes:
Auditory (hear)
Visual (sight)
1. Intense emotions Tactile (touch)
2. Suggestion Gustatory (taste)
Olfactory (smell)
3. Disorders of sense Organs
4. Sensory deprivation
5. Disorders of CNS
1. Emotions:
Depressed patients with delusions of guilt; hallucination tends to be disjointed or short
phases.
Occurrence of continuous persistent hallucinatory voices in severe depression should
arouse the suspicion of schizophrenia or some indercurrents physical disease.
Perception and culture
Specific learning experiences, memories, motives, and emotions of the individual also can
< influence perception
• Cultural factors can influence certain aspects of perception, including pictures perception
and susceptibility to illusions
2. Suggestion:
Normal subjects can be made to hallucinate.
Hypnotic hallucinations do not produce objective effects similar to those produced by
ordinary perceptions such as complimentary after images and so on
3. Disorders of sense Organs:
Hallucinatory voices may be heard in ear disease.
Visual hallucination is seen in eye diseases but usually there is disorder of
the CNS as well.
Peripheral lesions of sense organs may play a part in hallucinations in
organic states.
4. 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.
5. Disorders of CNS:
Lesions of diencephalons and cortex can produce hallucination that are not only visual
but can be auditory.
COMMON TESTS FOR PERCEPTION
Test
visuomotor task of leather lacing.
1) Structured
Observational
Test of Function
Consists of a screening test, neuropsychological checklist, and four ADL scales (eating from a bowl,
pouring a drink and drinking, putting on an upper body garment, and washing and drying hands).
2) Allen
Cognitive Level
to gain information concerning the client's educational and work background, the client is observed
performing the
3) The Behavioural To check client's ability to perform everyday
occupations. It consists of 9 activity-based subtests ana
(unilateral visual 6 pen & paper subtests.
