Face Recognition: Impairments in Prosopagnosia
Prosopagnosia, also called face blindness, is a neuropsychological condition that refers to impairment in the recognition of faces. Although prosopagnosic patients suffer from other types of recognition impairments (place recognition, car recognition, facial expression of emotion, est.), they experience face recognition problems above or over other types impairments. Prosopagnosia occurs without intellectual, sensory or cognitive impairments; in other words, people with prosopagnosia can still recognize people from non-facial cues. They cannot recognize familiar people by their faces alone, and often use alternative routes to alleviate the effects of this impairment. These routes include using voice, gait, clothing, hairstyle, and other information rather than faces. Not surprisingly, prosopagnosia can be socially crippling. In absence of these non-facial cues failures of recognizing familiar faces reveal; in fact, patients are unable to recognize famous people, close friends, family members, and even their images in the mirror.
Bodamer, a German neurologist, coined the term prosopagnosia in 1947 (Ellis & Florence, 1990). The word prosopagnosia is a combination of Greek word for face (prosopon) and the medical term for recognition impairment (agnosia). Bodamer also stated prosopagnosia was related to brain injury (head trauma, stroke, and degenerative disease), which refers to acquired prosopagnosia. People with acquired prosopagnosia had normal face recognition ability and then that was impaired. In contrast, prosopagnosia can occur from birth with no medical record of brain damage, which refers to pure developmental or congenital prosopagnosia.
Prosopagnosia is classified as face recognition impairment and differentiated from other types of impairments that can compromise face recognition (Young, 1992). People with prosopagnosia can achieve recognition using non-facial cues. In contrast, Young (1992) described patient K.S. was poor at recognizing people from faces and names. Her problem was considered as impairments of retrieval semantic information about the identities of individuals. Prosopagnosia is not a unitary syndrome, and different patients may show different types of recognition impairments. Bruce & Young (1986) claimed there were correspondences between these different types of recognition impairments and breakdown at different stages or levels of recognition.
Neural correlates of prosopagnosia
In the original view, prosopagnosia is acquired during adulthood or more rarely during childhood development, and it underlies brain injury. In general, prosopagnosia is thought to be associated with lesions of ventral occipitotemporal regions (Damasio et al., 1982). It has been suggested that unilateral lesions of the right cerebral hemisphere is more associated with prosopagnosia than the left side (Damasio et al., 1982; Farah, 1990). An earlier opinion is that relatively small numbers of prosopagnosics have bilateral lesions that are from autopsy reports (Damasio et al., 1982). However, later attitude is that lesion extent is probably underestimated, and more cases may have bilateral lesions because of limited resolution of brain images techniques (Farah, 1990). Although these two points of view are different, some cases show people with bilateral lesions were diagnosed as prosopagnosia. For example, patient FE (Bobes et al., 2004) suffered a close head trauma that produced bilateral lesions. He recovered but lost the ability to recognize familiar people by their faces alone. The extent of his brain lesions was identified by magnetic resonance imaging (MRI). The extensive bilateral damage in ventral occipitotemporal area was more severe on the right side. This case suggests that brain is an interconnected organ, and the right part of brain may play a more important role in prosopagnosia.
Recently developmental prosopagnosia is given more attention....
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