Prosopagnosia, also known as face blindness, is a cognitive disorder of face perception in which the ability to recognize familiar faces, including one's own face (self-recognition), is impaired, while other aspects of visual processing (e.g., object discrimination) and intellectual functioning (e.g., decision-making) remain intact. The term originally referred to a condition following acute brain damage (acquired prosopagnosia), but a congenital or developmental form of the disorder also exists, with a prevalence of 2–2.5%. Prosopagnosia should not be confused with prosopometamorphopsia, a disorder characterized by altered perceptions of faces.
Etymology Prosopagnosia is a medical Latin term adopted in 1948 into English from the German Prosopagnosie. It is derived from the Greek prosopon, 'face', and agnosia, 'ignorance'. The latter is formed from a-, 'not', and gnōstos, '(to be) known'.
Physiology The brain area usually associated with prosopagnosia is the fusiform gyrus, which activates specifically in response to faces. The functionality of the fusiform gyrus allows most people to recognize faces in more detail than they do similarly complex inanimate objects. For those with prosopagnosia, the method for recognizing faces depends on the less sensitive object-recognition system. The right hemisphere fusiform gyrus is more often involved in familiar face recognition than the left. It remains unclear whether the fusiform gyrus is specific for the recognition of human faces or if it is also involved in highly trained visual stimuli. Under normal conditions, prosopagnosic patients are able to recognize facial expressions and emotions. Acquired prosopagnosia results from occipital-temporal lobe damage and is most often found in adults. It is subdivided into apperceptive and associative prosopagnosia. Degenerative prosopagnosia is a form of acquired prosopagnosia that stems from a degenerative disease such as Parkinson's, Alzheimer's, or posterior cortical atrophy. In congenital prosopagnosia, a person never adequately develops the ability to recognize faces, and areas such as the right fusiform gyrus are underdeveloped, likely due to a genetic predisposition. Prosopagnosia as a whole tends to last throughout one's life. This is especially true of congenital prosopagnosia.
Treatment There are no widely accepted treatments. Though there have been several attempts at remediation, no therapies have demonstrated lasting improvements across a group of prosopagnosics. Prosopagnosics often learn to use "piecemeal" or "feature-by-feature" recognition strategies. This may involve secondary clues such as clothing, gait, hair color, skin color, body shape, and voice.
Implications Because the face seems to function as an important identifying feature in memory, it can be difficult for prosopagnosics to keep track of information about people and socialize normally. Prosopagnosia leads to social challenges, as inability to recognize faces can be misinterpreted as lack of interest in others. Using visual or auditory cues in place of facial recognition is unreliable and tiring. The condition can also be emotionally strenuous to mask, increasing the likelihood of social anxiety and depression. Prosopagnosia has also been associated with other disorders associated with nearby brain areas: left hemianopsia (loss of vision from left side of space, associated with damage to the right occipital lobe), achromatopsia (a deficit in color perception often associated with unilateral or bilateral lesions in the temporo-occipital junction), and topographical disorientation (a loss of environmental familiarity and difficulties in using landmarks, associated with lesions in the posterior part of the parahippocampal gyrus and anterior part of the lingual gyrus of the right hemisphere).
Types
Apperceptive Apperceptive prosopagnosia has typically been used to describe cases of acquired prosopagnosia with some of the earliest processes in the face perception system. The brain areas thought to play a critical role in apperceptive prosopagnosia are right occipital temporal regions. People with this disorder cannot make any sense of faces and are unable to make same–different judgments when presented with pictures of different faces. They cannot recognize familiar or unfamiliar faces. In addition, apperceptive sub-types of prosopagnosia struggle to recognize facial emotion. But some can recognize people by non-face clues, such as clothing, hairstyle, skin color, or voice. Apperceptive prosopagnosia is believed to be associated with impaired fusiform gyrus. Experiments on the formation of new face detectors in adults on face-like stimuli (learning to distinguish cats' faces) indicate that such new detectors are formed not in the fusiform but in the lingual gyrus.
Associative Associative prosopagnosia has typically been used to describe cases of acquired prosopagnosia with spared perceptual processes but impaired links between early face perception processes and the semantic information humans hold about people in our memories. Right anterior temporal regions may also play a critical role in associative prosopagnosia. People with this form of the disorder may be able to tell whether photos of people's faces are the same or different and derive the age and sex 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. Associative prosopagnosia is thought to be due to impaired functioning of the parahippocampal gyrus.
… excerpt ends here. Continue reading the full article.
