The brain conditions that interact with how it understands or processes the information from the senses are called agnosias. These diseases usually occur when vision or hearing works properly but your brain cannot process the information. In such cases, it leads to a disruption of the ability to understand or navigate.

What is Agnosia?

A condition in which the brain cannot recognize something even your senses detect it, is called agnosia. Furthermore, these brain diseases can also affect your senses including vision, hearing, smell, taste, and touch.

Agnosias can also impact your brain’s ability to make sense of information. For instance, an individual is not able to determine whether an object is moving or not while can identify the object when it is standing.

This group of brain conditions can impact anyone but older people are more likely to develop it.

How Common are Agnosias?

Generally, these brain diseases are very rare. Approximately 1% of people with neurological disorders have any type of agnosia.

What is the Difference between Aphasia and Agnosia?

These brain diseases have some similar characteristics but impact the brain differently. Check below some examples:

  • A condition in which the senses work properly but the brain cannot recognize one of them is called agnosia.
  • The brain disease in which a disruption of your language abilities occurs is called aphasia. Moreover, several aphasia types can happen. Some of them slow down speaking, make it harder to pronounce the right word, or even not speak at all.


There are two forms of agnosia and the symptoms depend on which one a person experiences. For example:

  • Apperceptive – This agnosia form occurs when senses work well but the brain cannot process the information.
  • Associative – People with this agnosia form pick up information and the brain processes it but they cannot recognize or make sense of information.

While between these agnosia forms are little differences they are important. For example, if multiple copies of the same picture are shown to people with agnosia, they know what a cat is but at the same time cannot recognize them by sight.

Agnosias Types

Visual Agnosias

  • Akinetopsia – A person cannot recognize moving objects.
  • Alexia – This agnosia type impacts the ability to read.
  • Amusia
  • Autopagnosia – This type impacts the ability to recognize body parts, no matter yours or other people.
  • Achromatopsia – An agnosia type in which you cannot identify the color. It is also known as color agnosia.
  • Cortical blindness – This agnosia type occurs when a person experiences an injury to the brain part that is responsible for visual input. Thereafter, your brain cannot process the signals sent from your eyes.
  • Environmental agnosia – People with this agnosia type are not able to describe the location they are or give directions to it.
  • Topographical agnosia – A person cannot remember the building’s layout or its surroundings.
  • Form agnosia – In such cases, people cannot recognize the object itself. For instance, they identify the wheels, seats, and handlebars of a bicycle when looking at each part but cannot recognize them as a part of a whole bicycle.
  • Simultagnosia – There are two types of this agnosia (including dorsal simultanagnosia and ventral simultanagnosia). When someone experiences dorsal simultanagnosia, they can see only one object at a time. If you are not focusing on an object, you cannot see it. However, those who suffer from ventral simultanagnosia can see multiple objects but recognize just one of them.
  • Prosopagnosia – This type of agnosia also has two types. For example apperceptive prosopagnosia and associative prosopagnosia. When you cannot recognize facial expressions or other nonverbal cues, you experience apperceptive prosopagnosia but if you cannot recognize a person’s face at all, it is associative prosopagnosia. In the second type, people usually recognize others by voice or other familiar sound. The main causes of prosopagnosia are brain damage and congenital (you are born with it).
  • Social-emotional agnosia – This type of agnosia usually occurs when a person cannot recognize nonverbal cues (such as body language). Social-emotional agnosia is very similar to apperceptive prosopagnosia but involves the body not only the face.

Auditory Agnosias

  • Amusia – In such cases, people cannot recognize songs or melodies they knew before.
  • Auditory agnosia – People with this agnosia type cannot recognize sounds despite good hearing. There are two types of auditory agnosia such as verbal auditory agnosia (also known as “word deafness”) and nonverbal auditory agnosia.
  • Cortical deafness – This is similar to cortical blindness, you can receive sounds and send them to the brain but it cannot process those sounds due to damage.
  • Phonagnosia – Familiar voices cannot be recognized by people with this type of agnosia.

Tactile Agnosias

  • Ahylognosia – It is not possible to determine the object’s properties such as weight, density, texture, and others.
  • Amorphognosia – You cannot determine the shape or size of an object.
  • Astereognosis – People with this agnosia type are not able to identify an object by feeling but know what the object is by looking at it.

Other Agnosias

  • Anosognosia – In such cases, an individual is not able to recognize he/she has a health condition. For example, if you have Parkinson’s disease and experience uncontrolled movements, you do not understand you have this health condition.
  • Anosodiaphoria – In such cases, you can recognize a health condition but do not understand its severity.
  • Gustatory agnosia – It is not possible to recognize types of tastes.
  • Olfactory agnosia – You cannot recognize some smells you previously recognized.
  • Unilateral neglect – People with this agnosia type usually cannot recognize any sensory input on one side of the body. It usually happens due to a lesion on the opposite brain site.


As we know brain problems are agnosias, not the senses themselves. This health condition is usually caused by a lesion in different parts of the brain. Check below some causes of brain lesions. Examples include:

  • Alzheimer’s disease
  • Aneurysms
  • Brain tumors (including both cancerous and noncancerous)
  • Dementia
  • Developmental disorders
  • Head injuries (such as concussions, traumatic brain injuries-TBIs)
  • Cerebral hypoxia (a lack of oxygen causes brain damage)
  • Infections (including those that provoke encephalitis)
  • Sleep apnea
  • Stroke
  • Toxins (carbon monoxide poisoning)
  • Seizures
  • Epilepsy

Additionally, this health condition is not contagious. However, some infections that could provoke agnosias are contagious but this disease occurs due to infections very rare.


To diagnose this condition, doctors perform a combination of physical examination, questions about your history, diagnostic imaging and tests, and others. First, physicians usually perform the following tests to ensure the following:

  • Sensory tests – These tests help to understand if your senses work correctly.
  • Cognitive and mental status check – During these procedures, your doctor will determine whether you have mental problems or not.
  • Memory and familiarity tests – Your doctor may perform these tests to verify if you have memory problems.
  • Diagnostic and imaging tests – These tests help to determine if you have damage or lesions to a specific part of the brain.

Doctors may perform other tests that will help to confirm this disease. Examples include:

  • CT (computed tomography) scans
  • Electroencephalogram (EEG)
  • Evoked potential test
  • MRI (magnetic resonance imaging)
  • Spinal tap (lumbar puncture)

Discuss with your doctor for more details.


Agnosia itself is not curable but the underlying condition can be. Therefore, doctors can treat this condition by focusing on the underlying problem. Check below some treatment options:

  • Medicines – Usually, doctors prescribe antibiotics for infections and antidementia drugs.
  • Surgery – In some cases, agnosia can be provoked by a tumor that puts pressure on certain areas in the brain. Removing the tumor can lessen the pressure in the brain.
  • Therapy and Rehabilitation – In most cases, agnosia is a permanent brain condition. These treatment options involve learning how to compensate or work when you have agnosia.

Frequently Asked Questions

Is it possible to prevent agnosia from developing?

There are some diseases that cause agnosias that cannot be prevented. However, certain conditions that provoke agnosias can be prevented. Check below some tips that will help prevent some health conditions that lead to agnosia:

  • Treat your infections
  • Wear safety equipment to prevent head injuries
  • Manage existing diseases
  • Adopt a healthy diet
  • Maintain a healthy weight

How long does an agnosia last?

While most agnosias are permanent, the duration depends on the type and severity of agnosia.

When should I go to the emergency room (ER)?

If you experience the following symptoms, you should go to the nearest ER right away. Examples include:

  • Swallowing problems
  • Trouble focusing, thinking, or concentrating
  • Sudden headache
  • Slurred or garbled speech
  • Weakness
  • Numbness
  • Paralysis
  • Confusion
  • Irritability
  • Agitation
  • Droop on one side of the face
  • Vision loss

In case you have any other questions, ask your healthcare professional.

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