1.(MeSH)The inability to recognize a familiar face or to learn to recognize new faces. This visual agnosia is most often associated with lesions involving the junctional regions between the temporal and occipital lobes. The majority of cases are associated with bilateral lesions, however unilateral damage to the right occipito-temporal cortex has also been associated with this condition. (From Cortex 1995 Jun;31(2):317-29)
definition of Wikipedia
Agnosia, Agnosia for Pain, Agnosia for Smell, Agnosia for Taste, Agnosia for Temperature, Auditory Agnosia, Auditory Agnosia, Congenital, Body-Image Agnosia, Congenital Auditory Agnosia, Developmental Agnosia, Finger Agnosia, Ideational Agnosia, Olfactory Agnosia, Position Agnosia, Sensory Agnosia, Somatosensory Agnosia, Tactile Agnosia, Time Agnosia, Topographical Agnosia, Visual Agnosia, Visual Agnosia for Objects, Visual Disorientation Syndrome, Visuospatial Agnosia[Hyper.]
Prosopagnosia (n.) [MeSH]
|Classification and external resources|
Prosopagnosia (Greek: "prosopon" = "face", "agnosia" = "not knowing") is a disorder of face perception where the ability to recognize faces is impaired, while the ability to recognize other objects may be relatively intact. The term originally referred to a condition following acute brain damage, but a congenital form of the disorder has been proposed, which may be inherited by about 2.5% of the population. The specific brain area usually associated with prosopagnosia is the fusiform gyrus.
Few successful therapies have so far been developed for affected people, although individuals often learn to use 'piecemeal' or 'feature by feature' recognition strategies. This may involve secondary clues such as clothing, gait, hair color, body shape, and voice. Because the face seems to function as an important identifying feature in memory, it can also be difficult for people with this condition to keep track of information about people, and socialize normally with others.
Selective inabilities to recognize faces were reported throughout the 19th century, and included case studies by Hughlings Jackson and Charcot. However, it was not named until the term prosopagnosia was first used in 1947 by Joachim Bodamer, a German neurologist. He described three cases, including a 24-year-old man who suffered a bullet wound to the head and lost his ability to recognize his friends, family, and even his own face. However, he was able to recognize and identify them through other sensory modalities such as auditory, tactile, and even other visual stimuli patterns (such as gait and other physical mannerisms). Bodamer gave his paper the title Die Prosop-Agnosie, derived from Classical Greek πρόσωπον (prosopon) meaning "face" and αγνωσία (agnosia) meaning "non-knowledge".
The study of prosopagnosia has been crucial in the development of theories of face perception. Because prosopagnosia is not a unitary disorder (i.e., different people may show different types and levels of impairment), it has been argued that face perception involves a number of stages, each of which can be separately damaged. This is reflected not just in the amount of impairment displayed, but also in the qualitative differences in impairment that a person with prosopagnosia may exhibit. Prosopagnosia is usually acquired through extensive neurological damage
This sort of evidence has been crucial in supporting the theory that there may be a specific face perception system in the brain. This is counterintuitive to many people, as not everyone experiences faces as 'special' or perceived in a different way from other objects in the rest of the world.
A recent case report described a closely related condition called prosopamnesia, in which the subject, from birth, could perceive faces normally, but had a severely impaired ability to remember them.
It has also been argued that prosopagnosia may be a general impairment in understanding how individual perceptual components make up the structure or gestalt of an object. Psychologist Martha Farah has been particularly associated with this view. Recently, it has been shown that developmental prosopagnosia may be characterized by a delay in processing of low spatial frequency information in faces.
Until late in the 20th century, prosopagnosia was thought to be quite rare and solely associated with brain injury or neurological illness affecting specific areas of the brain. However, recently a form of congenital prosopagnosia has been proposed, in which people are born with an impairment in recognizing and perceiving faces, as well as other objects and visual scenes.
Dr Jane Whittaker, writing in 1999, described the case of a Mr. C. and referred to other similar cases (De Haan & Campbell, 1991, McConachie, 1976 and Temple, 1992). The reported cases suggest that this form of the disorder may be heritable and much more common than previously thought (about 2.5% of the population may be affected), although this congenital disorder is commonly accompanied by other forms of visual agnosia, and may not be "pure" prosopagnosia. It has been suggested that very mild cases of face blindness are much more common, perhaps affecting 10% of the population, although there have not been any studies confirming this. The inability to keep track of the identity of characters in movies is a common complaint.
A classic case of a prosopagnosia is presented by "Dr. P." in Oliver Sacks' 1985 book The Man Who Mistook His Wife for a Hat, though this is more properly considered "agnosia." Although Dr. P. could not recognize his wife from her face, he was able to recognize her by her voice. His recognition of pictures of his family and friends appeared to be based on highly specific features, such as his brother's square jaw and big teeth.
Apperceptive prosopagnosia is thought to be a disorder of some of the earliest processes in the face perception system. People with this disorder cannot make any sense of faces and are unable to make same-different judgments when they are presented with pictures of different faces. They may also be unable to work out attributes such as age, gender or race from a face. However, they may be able to recognize people based on non-face clues such as their clothing, hairstyle or voice.
Associative prosopagnosia is thought to be an impairment to the links between early face perception processes and the semantic information we hold about people in our memories. People with this form of the disorder may be able to say whether photos of people's faces are the same or different and derive the age and gender from a face (suggesting they can make sense of some face information) but may not be able to subsequently identify the person or provide any information about them such as their name, occupation, or when they were last encountered. They may be able to recognize and produce such information based on non-face information such as voice, hair, or even particularly distinctive facial features (such as a distinctive moustache) that do not require the structure of the face to be understood. Typically such people do not report that 'faces make no sense' but simply that they do not look distinctive in any way.
Developmental prosopagnosia (DP) is a face-recognition deficit that is lifelong, manifesting in early childhood, and that cannot be attributed to acquired brain damage. However, a number of studies have found functional deficits in DP both on the basis of EEG measures and fMRI. It has been suggested that a genetic factor is responsible for the condition. The term “hereditary prosopagnosia” was introduced if DP affected more than one family member, essentially accenting the possible genetic contribution of this condition. To examine this possible genetic factor, 689 randomly selected students were administered a survey in which seventeen developmental prosopagnosics were quantifiably identified. Family members of fourteen of the DP individuals were interviewed to determine prosopagnosia-like characteristics, and in all fourteen families, at least one other affected family member was found.
There seem to be two categories of DP patients:
The first group of patients fail to obtain view-centered descriptions. According to the Bruce and Young model of face recognition, these are precursors of the more abstract expression-independent descriptions. View-centered descriptions do not seem to be specific for faces, as the patients with impairments of processing the physical aspects of faces also show difficulties in non-facial tasks like object recognition or tests of visuo-spatial abilities. However, there is as yet only limited evidence for a classification into different subtypes.
There are many developmental disorders that incorporate within themselves an increased likelihood that the person will have differences in face perception, of which the person may or may not be aware. That is to say, the person may or may not have insight in the clinical sense of the word. However, the mechanism by which these effects take place is largely unknown. A partial list of some disorders that often have prosopagnosiac components would include nonverbal learning disorder, Williams syndrome, and autism spectrum disorders in general. However, these types of disorders are very complicated, so arbitrary assumptions should be avoided.
One particularly interesting feature of prosopagnosia is that it suggests both a conscious and unconscious aspect to face recognition. Experiments have shown that when presented with a mixture of familiar and unfamiliar faces, people with prosopagnosia may be unable to successfully identify the people in the pictures, or even make a simple familiarity judgement ("this person seems familiar / unfamiliar"). However, when a measure of emotional response is taken (typically a measure of skin conductance), there tends to be an emotional response to familiar people even though no conscious recognition takes place.
This suggests emotion plays a significant role in face recognition, perhaps unsurprising when basic survival (particularly security) relies on identifying the people around you.
It is thought that Capgras delusion may be the reverse of prosopagnosia. In this condition people report conscious recognition of people from faces, but show no emotional response, perhaps leading to the delusional belief that their relative or spouse has been replaced by an impostor.
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Developmental prosopagnosia can be a difficult thing for a child to both understand and cope with. Many adults with developmental prosopagnosia report for a long time they had no idea that they had a deficit in face processing, unaware that others could distinguish people solely on facial differences.
Children with prosopagnosia can be hard to find. They may just appear to be very shy or slightly odd due to their inabilities to recognize faces. Children with prosopagnosia may have a hard time making friends, as they may not recognize their classmates. They often make friends with children with other distinguishing features.
Children with prosopagnosia may also have difficulties following the plots of television shows and movies, as they have trouble recognizing the different characters. They tend to gravitate towards cartoons, where the characters always wear the same thing and have other distinguishing features. Prosopagnosiac children may also have a hard time telling family members apart or recognizing people out of context (e.g., the teacher in a grocery store).
Additionally, those children with prosopagnosia can have a difficult time with the public school system, as many school professionals are not well versed in prosopagnosia, if they are aware of the disorder at all.
One of the goals of the Yonas Perception Lab (University of Minnesota) is to draw public attention to this disorder, in order to better educate school professionals on the topic so that children can receive appropriate interventions and assistance.
In conjunction with Dr. Ken Nakayama (Harvard University) and Dr. Brad Duchaine (University College London), the lab is conducting research on prosopagnosia in children. Their goals are to better understand the development of face processing in children, create more appropriate tests for the disorder, study treatment in individuals with prosopagnosia, and raise awareness about the disorder.
In 2005, a study led by Ingo Kennerknecht showed support for the proposed congenital disorder form of prosopagnosia. This study provides epidemiological evidence that congenital prosopagnosia is a frequently occurring cognitive disorder that often runs in families. The analysis of pedigree trees formed within the study also indicates that the segregation pattern of hereditary prosopagnosia (HPA) is fully compatible with autosomal dominant inheritance. This mode of inheritance explains why HPA is so common among certain families (Kennerknecht et al. 2006).
|Look up prosopagnosia in Wiktionary, the free dictionary.|
|Wikiversity has learning materials about Prosopagnosia|
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