Agnosia is an acquired recognition disorder. Linked to the interpretation of sensory information, this disorder can affect different senses including sight (visual agnosia), hearing (auditory agnosia) and touch (tactile agnosia).

Agnosia is a gnotic disorder, that is to say a disorder of recognition. An agnosic person cannot recognize a known object, sound, smell or face.

Agnosia is distinguished from other gnotic disorders by the absence of primary sensory deficit. In other words, an agnotic person has normal sensory functions. The origin of agnosis disorders is linked to the transmission and / or interpretation of sensory information. In the brain, an alteration of sensory memory can explain the appearance of certain agnotic disorders.

Agnosis disorders usually involve only one sense. The most frequent forms are visual, auditory and tactile agnosias.

The case of visual agnosia

Visual agnosia is when a person is unable to recognize certain familiar objects, shapes or signs by sight. However, visual agnosia should not be confused with a visual impairment, which is characterized by a decrease in visual acuity.

Depending on the case, visual agnosia can be linked to a problem in the interpretation of information concerning space, shapes, faces or even colors. As such, it is possible to distinguish:

• agnosia of objects which may be associated with associative agnosia with an inability to name an object present in the visual field, or apperceptive agnosia with an inability to name and draw an object present in the visual field;
• prosopagnosia which concerns the recognition of known faces, both that of close people and one’s own face;
• agnosia of colors which is characterized by an inability to name the different colors.

The case of auditory agnosia

Auditory agnosia results in the inability to recognize certain known sounds. Depending on the case, it is possible to distinguish:

• cortical deafness which is characterized by an inability to recognize known sounds, familiar noises or even music;
• la verbal deafness which corresponds to an inability to understand spoken language;
• the fun which designates an inability to identify the melodies, rhythms and timbres of voices.

The case of tactile agnosia

Also called astereognosia, tactile agnosia is characterized by an inability to recognize an object by simple palpation. This recognition disorder can concern the material, weight, volume or even the shape of the object.

The special case of asomatognosia

Asomatognosia is a special form of agnosia. It is characterized by a loss of recognition of part or all of his body. Depending on the case, it is possible to distinguish:

• theautotopoagnosie which characterized by an inability to recognize different parts of his body;
• thedigital agnosis, which concerns only the fingers.

Agnosis disorders can have different explanations. They are often due to the appearance of brain damage following:

• un stroke (Stroke), sometimes called a stroke, which is caused by a problem with the blood flow to the brain;
• un head trauma, a shock to the skull which can cause brain damage;
• neurological disorders, including dementia and neurodegenerative diseases such as Alzheimer’s disease;
• a brain tumor which results in the development and multiplication of abnormal cells in the brain;
• a brain abscess, or abscess of the brain, which can be the result of different infections.

The consequences and course of agnosia depend on many parameters including the type of agnosia, the cause of the symptom and the patient’s condition. Agnosic disorders cause discomfort in daily life which can be more or less important depending on the case.

Treatment involves treating the cause of agnosia. It depends on the diagnosis, which is usually carried out by clinical examination and supplemented by extensive medical examinations. In particular, neuropsychological examinations and cerebral medical imaging analyzes may be carried out to confirm the diagnosis.

Treatment of agnosia is usually accompanied by rehabilitation to improve the quality of life of people with agnosia. This rehabilitation can involve different specialists including occupational therapists, speech therapists and physiotherapists.