Agnosia: Causes, Types, and Outlook

January 1, 2023

The term “agnosia” refers to a collection of diseases in which injury to the brain makes it difficult for the individual to absorb or understand the information received from their senses.

Your brain cannot process the information, even though your senses, such as vision and hearing, are functioning normally. Because of this, you may need help comprehending or navigating the world around you.

What is Agnosia?

There is a category of conditions known as agnosias in which a person’s brain cannot perceive something, even though their senses can detect it. A variety of your senses, including sight, hearing, smell, taste, and touch, may be impacted due to the disorders.

Additionally, they can hinder the capacity of your brain to organize and make sense of the information you take in. A good illustration of this would be the inability to recognize that a moving thing is the same object you can realize while it is still in its original position.

Who Does it Affect?

Agnosia can affect people of any age, but it most commonly arises due to specific illnesses that affect the brain.

How Common is this Condition?

Agnosias are relatively infrequent overall. Agnosia can take many forms, but its prevalence among patients undergoing treatment for neurological (brain) conditions is extremely low (less than 1 percent).

How Does this Condition Affect My Body?

Agnosias are conditions that cannot be explained away as problems with a person’s senses or memory and so cannot be treated in the same way.

One person who fits this description is aware of the presence of a cat in the room with them but is unable to recognize the animal based on its appearance (a person who suffers from visual agnosia, for instance) or who is unable to tell from the animal’s meow that it is a cat (auditory agnosia).

What's the Difference Between Agnosia and Aphasia?

Now, what is agnosia, and how does it differ from aphasia?

Agnosia and aphasia are two highly distinct conditions, although they share some similarities.

Both involve damage to a portion of your brain, but how that damage manifests itself in your brain is distinct for each. The following are the key distinctions:

Damage to the brain can cause a disease known as agnosia, in which the individual cannot recognize information coming in from any of their senses, including their sight, hearing, etc. Your senses usually function, but the area of your brain responsible for processing the sensory information is not.
Aphasia is a disorder in which injury to some areas of the brain disrupts a person’s verbal ability. A variety of aphasias can cause a person’s speech slurred or slowed down, make it more challenging to select or correctly pronounce the appropriate word, or even prevent them from speaking.

Specific Types of Agnosias

A few examples of distinct sorts of agnosias are as follows:

Visual (sight) agnosias

Akinetopsia is a condition in which a person can detect objects but is unable to recognize that those objects are moving.
Alexia: Those affected by this ailment are unable to read. They can continue seeing the words and have no difficulty communicating verbally or in writing.
Because of the visual effect of this issue, you will lose the capacity to read music, known as amusia (see the auditory impact below).
Autopagnosia is a condition in which a person has difficulty distinguishing different portions of their own body or other people’s bodies. You may also have problems identifying body parts based on an image or drawing of them. Finger agnosia is a subtype of this condition. If you have this condition, you know what fingers are but cannot recognize them when you see them.
Achromatopsia is a condition in which a person can see colors and differentiate between them, but they cannot name the color. This condition is also known as color agnosia.
Your eyes are functioning normally, but your brain is unable to interpret the signals that are being supplied to it from your eyes.
Environmental agnosia is a condition in which a person cannot recognize their current location, describe a familiar place, or give instructions to that place.
One subcategory of environmental agnosia is known as topographical agnosia. If you have this condition, it indicates that you can recall the particulars of a building’s plan or its surroundings. Still, you need to determine where you are concerning the layout and navigate your way about the building.
Form agnosia is a condition in which a person can see the components of an object but cannot identify the thing itself. An illustration of this would be being able to recognize the individual components of a bicycle, such as the wheels, seat, and handlebars, but being unable to place those components within the context of the entire bicycle.
Simultagnosia is a condition in which a person has difficulty seeing more than one of the same things simultaneously.

Manifestations of Agnosia

There are many different manifestations of this illness. The inability to see more than one thing at a time is called dorsal simultanagnosia. You cannot perceive an object if your attention is not focused on it. In the condition known as ventral simultanagnosia, a person can perceive many things simultaneously but can only identify them one at a time.

This disorder, which has two subtypes and is also known as “face blindness,” is referred to as prosopagnosia. Apperceptive prosopagnosia is a condition in which a person cannot identify other people’s facial expressions or other nonverbal signs. The condition known as associative prosopagnosia is when a person cannot recognize the face of a familiar person even though they are familiar with the individual. Congenital means that someone is born with the condition. The most common cause of this disorder is an injury to the brain, which can also be present at birth. People born with this condition always have difficulty recognizing people’s faces. Because congenital prosopagnosia can often be found in families, it is probably a hereditary condition.
A person is said to have social-emotional agnosia if they cannot comprehend nonverbal signs such as body language. It is similar to apperceptive prosopagnosia (which you can read about right above), except that it affects an individual’s entire body rather than their face.

Auditory (sound) agnosias

The aural symptom of this condition is that you cannot recognize tunes or melodies that you were previously familiar with. In addition, you may have trouble differentiating music from other noises or identifying individual musical notes.

Auditory agnosia is a condition in which a person cannot recognize sounds, even though they can hear them quite well. There are many distinct variations of this regarding the sounds that humans make. When someone has verbal auditory agnosia, they cannot perceive words uttered aloud.

This condition is often referred to as “word deafness.” You can still read and write them and have no difficulty communicating verbally with others.

People with nonverbal auditory agnosia can hear the words that other people speak, but they cannot recognize the sounds that other people make.

Cortical deafness is an issue with some portions of your brain, similar to cortical blindness, which affects your vision.

Your ears can pick up noises and transmit information about those sounds to your brain. On the other hand, because of injury to particular brain regions, your brain cannot process such messages.

People with this sort of phonagnosia cannot distinguish known voices, yet they are perfectly capable of understanding what someone is saying when they hear a familiar voice.