Although prosopagnosia has been frequently documented in adults, recent research has given added attention to deficits in facial recognition in children. One such patient, identified as K.D., sustained cerebral damage in infancy and since had been unable to recognize people’s faces (Young & Ellis, 1989). However, when tested at ages 8-11 her visual abilities were found to be somewhat impaired, but were no poorer than other children who could recognize faces with no difficulty. She was diagnosed with prosopagnosia, where she could identify a face for what it was, can perceive and imitate facial expressions, but she does not have a recognition of faces that should be familiar to her due to previous experiences with them. It is believed that 2-2.9% of the general population is affected by face recognition difficulties (Bowles et al., 2009). Prosopagnosics use other cues such as voice, clothes, context and nonverbal cues to identify familiar people. This cognitive impairment is similar in both children and adults; with the exception that a child whose functional ability has been impaired at infancy has no memory of what it used to be like to recognize faces.
More recently theoretical models to explain face processing have been assembled using data from case studies of prosopagnosics. Initially face processing is analyzed in a way common to all objects, perceiving the size, orientation and figure-ground relationships (Brunsdon et al., 2006). Next the face is structurally encoded, including an abstract representation that integrates a global general configuration along with its individual unique features. Each feature, such as nose, mouth, ears are given a ‘feature value’ recognized as an individual nose, for example, associated with that person. Recognition occurs when a known individual feature value for each feature group is recalled that is associated with that person. This recall also brings to mind associated personality characteristics and facts about that person. Of course the same information can be recalled from nonfacial cues such as those already mentioned above. Face recognition can give other information about a person, such as facial expression and mood since some cues will be specific to the person and vary from the last time the facial information was processed. However, this model is likely oversimplified, as studies with inherited prosopagnosia have shown. Subjects belonging to the same family expressed a variety of impairments, indicating that prosopagnosia may not be a single trait but a cluster of related subtypes, with individuals having some variety of impairments to the face-processing system (Schmalzl et al., 2008). Another interesting point is that studies employing MRI scanning of the brain have shown that the brain does indicate a recognition of faces, but this is a covert recognition not consciously known by the subject (Jones & Tranel, 2001).
Research into treatment for prosopagnosia have indicated successes in training to teach face recognition (Francis et al., 2002). One study focused on training using a complex mnemonic, incorporating remembering a prominent facial feature, the person’s name and occupation in order to remember photographs of particular people. To relearn a familiar face, they rehearsed semantic information about the person while viewing their photograph. However the improvements in facial memory was person specific and not particular to the stimulus used. Brunsdon et al. were able to successfully treat an 8 year old child with prosopagnosia through studying photos and observing and discussing the major facial features, such as those associated with the eyes, nose, mouth and hair (2006). After an established baseline the child showed significant improvement continuing post treatment, as well as anecdotal evidence that his ability to identify family members had improved. The study identified recognition of eyes and mouth as being most important for face processing. In another study, a 4-year-old girl diagnosed with congenital prosopagnosia was tested by monitoring eye movement recordings when studying faces (Schmalzl et al., 2008). Results of the scans revealed that the child’s scan paths lay outside the internal core features, particularly away from the eye region. Previously the girl had tended to use hair and voice to for recognition cues. The study then turned to focusing the child’s training on directing visual attention to characteristics of the internal features of faces. This precise training was rapidly integrated by the child and showed improvements similar to the study by Brunsdon et al.
Although prosopagnosia affects both children and adults alike, there seems to be more we can learn from studying these cognitive deficits in children. It appears that the underlying problem tends to be with abnormal scan pathing in the prosopagnosic subjects, at least with regards to faces. The treatment seems to be clear, but there are still some questions that merit further study. Why do some children have this abnormal scan pathing? Is there some common reason for why this may be happening in some children but not others? Although in some cases there may be a genetic component, in developmental prosopagnosia environmental factors may contribute the most. Further studies should consider potential environmental effects or particular childhood experiences that could contribute to inducing developmental prosopagnosia. In congenital prosopagnosia, brain-imaging studies can reveal more detailed information about how visual components of the brain develop, and how the brain can correct these physical problems over time.
References
Bowles, D. C., McKone, E., Dawel, A., Duchaine, B., Palermo, R., Schmalzl, L., et al. 2009. Diagnosing prosopagnosia: Effects of ageing, sex and participant-stimulus ethnic match on the Cambridge Face Memory Test and Cambridge Face Perception Test. Cognitive Neuropsychology, 26, 423-455.
Brunsdon, R., Coltheart, M., Nickels, L. & Joy, P. 2006. Developmental prosopagnosia: A case analysis and treatment study. Cognitive Neuropsychology, 23, 822-840.
Francis, D., Riddoch, M. J., & Humphreys, G. W. 2002. “Who’s that girl?” Prosopagnosia, person-based semantic disorder, and the reacquisition of face identification ability. Neuropsychological Rehabilitation, 12, 1-26.
Jones, R. D. & Tranel, D. 2001. Severe developmental prosopagnosia in a child with superior intellect.
Schmalzl, L., Palermo, R. & Coltheart, M. 2008. Cognitive heterogeneity in genetically based prosopagnosia: A family study. Journal of Neuropsychology, 2, 99-117.
Schmalzl, L., Palermo, R., Green, M., Brundson, R. & Coltheart, M. 2008. Training of familiar face recognition and visual scan paths for faces in a child with congenital prosopagnosia. Cognitive Neuropsychology, 25, 704-729.
Young, A. W. & Ellis, H. D. 1989. Childhood prosopagnosia. Brain and Cognition, 9, 16-47.
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