Visual impairment in posterior cortical atrophy and dementia with lewy bodies

Abstract

Background: Posterior Cortical Atrophy (PCA) is a rare neurodegenerative disease associated with Alzheimer's disease pathology that presents with progressive deterioration in visual perception. Patients with PCA present with complex visual impairments such as Balint syndrome, Gerstmann syndrome, simultanagnosia, neglect and topographical disorientation. Dementia with Lewy bodies (DLB) is, similar to PCA, also characterised by profound impairments in visual perception. However, little is known about the nature underlying these complex visual deficits associated with both conditions. Methods: To investigate the nature of visual impairments, the present study compared PCA, DLB, and healthy control participants in visual tasks designed to measure the efficiency of the visual system at different levels of processing. In ascending order of complexity there were tasks of visual acuity, line orientation, contour integration, and rotated object comparison. Results: DLB patients did not differ from controls in visual acuity and line orientation, but were impaired in contour integration and object comparison. PCA patients were impaired in all tasks. Conclusions: In PCA all processing stages were affected, whereas DLB was only associated with deficits in contour integration and object comparison. We conclude that low level impairments affecting processing stages before the dorsal-ventral distinction contribute to visual deficits in PCA. In addition our results suggest that deficits in feature integration thresholds may contribute to object recognition impairments in DLB.