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Jonathan Marotta, Loni Desanghere, Benjamin Meek, Lee Baugh, Jane Lawrence, Keri Locheed, Paul Shelton; Posterior cortical atrophy: The effects on perception and action. Journal of Vision 2009;9(8):1095. doi: 10.1167/9.8.1095.
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© ARVO (1962-2015); The Authors (2016-present)
Posterior cortical atrophy (PCA) is a rare progressive neurodegenerative disorder that can target the occipital, temporal and parietal lobes. In early stages, PCA is characterized by impairments in higher level visual processing, while memory, language, and reasoning remain relatively intact. Symptoms can include problems in colour perception, face and object recognition, visually guided action, reading, writing, and problems seeing multiple objects in an array — depending on the location of atrophy. Here we present data from a 74-year-old woman, RB, who has been experiencing progressively worsening visual disturbances over the last 3 years.
RB shows severe deficits in recognizing faces (including gender and race) and line drawings of common objects and, despite being a talented artist, she now has difficulty reproducing even simple line drawings. In particular, her deficits involve problems with integrating factors into a concept of the whole — she focuses her attention on one aspect or one detail of the visual form and then is unable to use additional features to form a holistic representation. RB has also experienced colour “hallucinations” where, for example, she has seen walls as different colours after closing and reopening her eyes, or sees colour in black and white pictures.
Combined with MRI cortical analysis, these behavioural results suggest atrophy to the inferior temporal cortex, extending to the angular gyrus in the right hemisphere. Despite these severe perceptual difficulties, RB shows a relatively preserved ability in her visually guided action — properly scaling her grasp for object size and selecting stable grasp points on objects she is impaired at distinguishing perceptually. This case of “ventral” PCA reinforces the findings that there are separate visual pathways for visual perception and the visual control of action.
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