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Jonathan Marotta, Keri Locheed; Posterior Cortical Atrophy: The role of Simultanagnosia in deficits of Face Perception. Journal of Vision 2011;11(11):580. doi: 10.1167/11.11.580.
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© ARVO (1962-2015); The Authors (2016-present)
When viewing a face, healthy individuals tend to fixate on upper regions, particularly the eyes, which provide important configural information. In contrast, individuals with face blindness (prosopagnosia) rely more on local features–particularly the mouth. We have recently presented research on the neurodegenerative disorder posterior cortical atrophy (PCA), which is characterized by impairments in higher level visual processing – including face perception. Common among PCA patients is simultanagnosia, an inability to perceive more than one object or detail simultaneously. One might consider simultanagnosia the most extreme form of a feature-based approach. Do PCA patients produce gaze patterns similar to those associated with prosopagnosia? Or, do their patterns reflect even more of a simultanagnosia-based local dependence. Three PCA patients, RB, SS, and AP, and their healthy controls, completed a same/different discrimination task in which images of faces were presented as cue-target pairs. RB exhibits a “ventral” form of PCA, while SS and AP are more “mixed” or “dorsal” in presentation. Nevertheless, all three patients show signs of impaired face perception and simultanagnosia when tested, even though only RB has reported face perception problems in everyday life. In contrast to previous research with prosopagnosic patients, the PCA patients each produced unique scan paths that focused on one aspect of the face: the forehead for RB, the nose for SS, and the left cheek for AP. Surprisingly, the regions selected by the PCA patients often contained minimal contrast and little configural or feature-based information, suggesting that they were having difficulty processing the face even at a featural level. These results suggest a role of simultanagnosia in the gaze fixation patterns of PCA patients that is not reflective of ‘typical’ prosopagnosia, and instead point to simultanagnosia as an underlying cause of the face perception deficits seen in PCA.
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