This document provides information on various types of perception disorders, including visual, tactile, body schema, and motor perception disorders. It defines key terms like agnosia, apraxia, neglect and discusses how to assess deficits in areas like visual recognition, tactile identification, praxis, construction and more. Assessment involves tasks like identifying objects by sight or touch, naming fingers, copying designs, and demonstrating spatial understanding. Perceptual disorders can affect many daily living skills and safety.

1. RAVI RANJAN KUMAR
(OCCUPATIONAL THERAPIST)
MOT(JAMIA HAMDARD) NEW DELHI
BOT (NIOH)KOLKATA

2. Perception
• Perception is the mechanism by which the brain interprets
sensory information received from the environment.
• Perception is the gate away to cognition.
• This perceived information is then processed by the various
cognitive centers in the brain. The individual may then
choose to respond with a motor act or a verbal expression.
• In early development, tactile, proprioceptive, vestibular,
and visual perception provide an internalized sense of body
scheme, which is basic to all motor function.
• Severe perceptual deficits, frequently combined with
cognitive impairments, can affect every area of
occupation(e.g., activities of daily living [ADLs], education,
work, play, leisure, and social participation) and can present
with grave safety concerns.

4. Visual Perception
• Visual perception is the ability to interpret the surrounding
environment using light in the visible spectrum reflected by
the objects in the environment.
• This is different from visual acuity, which refers to how
clearly a person sees (for example "20/20 vision"). A person
can have problem with visual perceptual processing even if
he/she has 20/20 vision.
• Person with a visual perception disorder, impairs the
person’s ability to recognize and identify familiar objects
and people.
• These individuals also have difficulty interpreting the
meaning of objects in their environment, such as signs and
maps. In addition, they can have difficulty recognizing,
identifying, or remembering the names of colours in their
environment.

5. Types of visual perception dysfunctions
• Visual Agnosia-Inability to identify and recognize a common item using visual means.
Assessment is done by asking the person to identify five common objects by sights.
• Colour Agnosia- Inability to remember and recognize the specific colours for common
objects in environment. Assessment can be done by presenting two accurately coloured
and two not accurately coloured object and to pick the inaccurately coloured.
• Colour Anomia- inability to name the colour of an object correctly. The person
understands the difference between different colours but unable to name the colour of
object correctly.
• Metamorphopsia- refers to the visual distortion of objects, such as the physical properties
of size and weight. Assessment for metamorphopsia includes presenting the person with
various objects of different weights and sizes. Metamorphopsia may be indicated if the
person is unable to determine the weight and size of the various objects.
• Prosopagnosia- refers to an inability to recognize and identify familiar faces caused by
lesions of the right posterior hemisphere. Informal assessments could include having the
client identify the names of the people in photographs, with family members at a dinner
table or by having the person identify his or her own face in a mirror.
• Simultanognosia- refers to the inability to recognize and interpret a visual array as a
whole, and it is caused by lesions to the right hemisphere of the brain. The person is able
to identify the individual components of a visual scene, but are unable to recognize and
interpret the composition of the scene. Assessment includes presenting the person with a
photograph with a detailed visual array (e.g. family photograph at the beach), asking the
client to describe the scene in detail, and assessing whether or not the client can describe
the scene as a whole.

6. Visual-Spatial Perception Disorders
Visual-spatial perception refers to the capacity to appreciate the spatial arrangement of one’s body,
objects in relationship to oneself, and relationships between objects in space.
Types:
• Figure-Ground Discrimination-It allows a person to perceive the foreground from the background in a
visual array. But the dysfunction in it is the inability to visually distinguish a targeted object from the
background. It can be assessed functionally in a variety of contexts. During a dressing activity, you may
ask the client to identify the white undershirt that is located on top of his or her white sheets. In the
kitchen, you can ask the client to pick out all of the spoons from a disorganized utensil drawer.
• Form-Constancy Dysfunction- Form constancy is the recognition of various forms, shapes, and objects,
regardless of their position, location, or size. Form-constancy dysfunction is the inability to identify
objects placed in an unusual position. To assess form constancy, the person is asked to identify familiar
objects in his or her environment through observation alone when those objects are placed upside down
or on their side in an unusual position.
• Spatial relation/ Position in space- it refers to the relative orientation of a shape or object to the self.
Spatial disorientation is the inability to perceive the relationship of an object in space to another or
oneself. To assess position in space, the person is asked place common objects in relation to the self or
other objects using the following directional terms: top/bottom, up/down, in/out, behind/in front of,
and before/after.
• Topographical disorientation- it refers to difficulty in understanding and understanding the relationship
of one location to another. It can be tested by asking to describe a familiar location or block he/she lives.

7. • Right left discrimination dysfunction- Right-left
discrimination is the ability to accurately use the
concepts of right and left. An individual with right-left
discrimination dysfunction may confuse the right and
left side of his or her body or confuse right and left in
directional terms when navigating through the
environment. To assess right-left discrimination,person
is asked to point to various body parts.
• Stereopsis- It is the inability to perceive depth in
relation to the self or in relation to various objects in
the environment. To assess this dysfunction person is
asked to fill a glass of water.

8. Tactile perception disorders
Inability to discriminate between different types of
materials or different forms and shapes by tactile means
and must compensate visually to determine the objects.
• Astereognosis- Inability of an individual to identify
common objects and geometric shapes through tactile
perception (touch) without the aid of vision. To assess it
person is asked to identify known objects through touch
with occluded vision.
• Agraphesthesia- It is the inability to recognize numbers,
letters, or forms written on the skin. To assess it person’s
vision is occlude and letters, numbers, or geometric forms
are traced on the fingertips or palm with a dull-pointed
pencil or similar instrument.

9. Body schema perception disorder
Distortion in a person’s sense of his or her body’s shape,
position, and capacity.
Types:
• Finger agnosia- inability to discriminate the fingers of hand.
it is evaluated by occluding the person’s vision and asking
him or her to name each finger as the therapist touches it.
• Unilateral neglect- it is the inability to report, respond or
orient to meaningful stimuli presented on the affected side
of body. It can be assessed by letter cancellation test or
draw a man test.
• Asomatognosia-inability to correctly identify parts of his or
her body parts.

10. Motor perception disorders
• Praxis- it is the ability to plan and perform purposeful movement.
• Apraxia-deficit in “the execution of learned movement which cannot be
accounted for by either weakness, incoordination, or sensory loss, or by
incomprehension of or inattention to commands.
Types:
• Ideational Apraxia-Inability to conceptualize, plan, and execute the
complex sequences of motor actions involved in the use of tools or
otherwise interacting with objects in everyday life.
• Ideomotor Apraxia- It is an inability to carry out a motor act on verbal
command or imitation. However, the person with ideomotor apraxia is
able to perform the act correctly when asked to use the actual object.
• Dressing Apraxia- Inability to plan effective motor actions required during
the complex perceptual task of dressing one’s upper and lower body.
• Constructional Apraxia-inability to organize or assemble parts into a
whole, as in putting together block designs (three-dimensional) or
drawings (two-dimensional).