Visual and spatial perception in the early phase of Alzheimer's disease

A battery of visuospatial perception tests was administered to 27 mild probable Alzheimer's disease (AD) patients; 21 were reassessed after 8 months. At the first evaluation, AD patients were impaired only in an object-naming task. After 8 months, the performance in the subtests of object perception was unchanged, while then was a significant decline in the total score of the items tapping space perception. A significant worsening was also observed in the Rey's figure copy score and was correlated with the decrease in the spatial perception score. This study confirms that an impairment in visual perceptual tests requiring access to semantic and lexical knowledge is present in the earliest phase of AD, whereas visuospatial and constructional impairments became evident only later. This pattern of progression may represent the clinical correlate of increasing pathological involvement of posterior associative cortex.