Agnosia.pdf..............................

Agnosia
Types of agnosia
Forms of agnosia
Criteria of agnosia
Causes of agnosia

1. Agnosia
Noorulain

2. Agnosia
- Gnosia ‘to know’, Agnosia ‘without knowledge’
-Referred to as soul blindness
-a rare disorder whereby a patient is unable to recognize and identify objects,
persons, or sounds using one or more of their senses despite otherwise normally
functioning senses.
-Exists alone or as a symptom of other disorders such as neurodegenerative
disorders
-Typically only one sensory pathway is affected

3. Criteria
-Failure to recognise an object
-Ability to name object once recognised (excluding language disorders such as
anomia as the main deficit)
-Absence of generalised dementia

4. Types
-Hearing (auditory agnosia): People cannot identify objects based on sound.
For example, they cannot identify a telephone when they hear it ring. This
type of agnosia results from damage to the temporal lobe.

-Taste (gustatory agnosia): People cannot identify tastes even though they can
experience them. This type results from damage to the temporal lobe.

-Smell (olfactory agnosia): People cannot identify odors even though they can
experience them. Olfactory agnosia may result from damage to the front part
of the temporal lobe.

5. Cont.
-Touch (somatosensory agnosia): For example, people have difficulty
identifying a familiar object (such as a key or safety pin) that is placed in their
hand. However, when they look at the object, they immediately recognize and
can identify it. This type of agnosia results from damage to the parietal lobe.

-Sight (visual agnosia): People cannot recognize common objects (such as a
spoon or a pencil) even though they can see these things, but they recognize
them when they touch the objects. Visual agnosia results from damage to the
occipital lobe.

6. Example
-An example of this is a person who knows what a cat is and can see that
there’s a cat in the room with them, but can’t tell you that it’s a cat by looking
at it (visual agnosia), or they can’t identify that it’s a cat from its meow
(auditory agnosia)

7. Object Agnosia Forms
-Apperceptive: This form involves a problem of perception although the visual functions
of color, motion are retained.
If you show multiple copies of a picture of a cat to a person with apperceptive agnosia,
they would be able to tell that it’s a cat, but they can’t tell that it’s the same picture.
-Bilateral damage to lateral parts of occipital lobe along the ventral stream
-Caused by carbon monoxide poisoning, harming watershed areas of the brain

8. Simultanagnosia
Dorsal simultagnosia: Patients cannot see more than one object at a time. For example, when
presented with a picture with a table, chair and flower vase, they may report only one thing at a
time. When their attention is diverted to the other thing, they can then identify only that thing;
other things disappear to them. They often have difficulty reading as it involves viewing more
than one word at a time. They often bump into objects that are close together. Dorsal
simultagnosia is typically associated with bilateral lesions in the occipital parietal junction
Ventral simultagnosia: These individuals also cannot identify more than one object or complex
objects at one time, although they can see more than one object at a time. They are unable to
perceive the whole picture as one and derive a meaning out of it. For example, in a night sky
picture with stars and full moon, they may identify the moon as a ball, unable to derive the
meaning of the whole picture. Ventral simultagnosia is associated with lesions in the left inferior
occipitotemporal junction.

9. Object Agnosia Forms
-Associative: This type is a problem of recognition. The senses can pick up information
and the brain can process it, but it can’t recognize or make sense of the information
coming in
If you show the same pictures to someone with associative agnosia, they would
recognize it’s the same picture, they would be able to draw it but wouldn’t be able to tell
that it’s a cat

10. Causes
-Damage to occipital, parietal or temporal lobe
-Stroke
-Brain injury
-Tumor
-Hypoxia
-Toxins
-Progressive neurodegenerative diseases (e.g Alzheimers)

11. Assessment
Sensory tests: These tests will make sure that the involved sense in question
works as it should and rule out any sense-related problems or conditions.
Cognitive and mental status check: These tests ensure the problem isn’t with the
person’s thinking, focusing or problem-solving abilities.
Memory and familiarity tests: These tests will verify that the person doesn’t have a
memory problem. They also make sure a person’s lack of recognition isn’t
because of a lack of experience or familiarity with something.
Diagnostic and imaging tests: These tests look for lesions or signs of damage to
the relevant part of your brain.

12. Rehabilitation
1)Restoration: aims to improve a particular function by training the impaired
function and thereby the damaged brain structure directly and repetitively
2)Compensation: refers to using an intact function to compensate for the loss
of the other one e.g:
- Developing auditory skills in prosopagnosia to help reocngise people
- In associative, placing signs in strategic areas of the home or kitchen to
prevent accident
- Use of greeble to improve object recognition (doesn’t show improvement in
face recognition)
-

13. PAINT model
-hierarchical reorganization of the cerebral cortex, composed of primary
(projection) areas responsible for receiving perceptual information, secondary
(association) areas tasked with combining stimuli to give them meaning, and
tertiary (integration) areas responsible for interpreting information in various
ways
-First stage: Stimulation of projection areas, addressing the most basic
aspects of visual perception, such as changes in light, size of "bumps," and
size of objects. Recognition of differences through other senses, such as
weight, volume, intensity of odor, or sound.

14. Cont.
-Second stage: stimulating association areas through the visual discrimination
of simple stimuli, such as color, shapes, and figures. The combination of
visual features that composed the stimulus are addressed, relying on memory
and language. Patients are asked to describe the shape, size, and texture,
with permission to smell, taste, and touch
-Third Stage: stimulating integration areas, relating the shape and
characteristics of the object to its name and position in space, and abstracting
the main features of the object to depict them with pencil and paper alongside
their name. In the two-dimensional plane, the drawings that the patient has to
create become progressively more abstract and complex. Letter and number
discrimination, reading, writing, and calculation are also addressed.