MENTAL ROTATION IN PATIENT AFFECTED BY DEMENTIA

Objectives. Many studies show an early presence of verbal deficit in dementia. Some studies report deficit in visuospatial task but the ability of mental rotation in subjects with cortical damage has been largely unstudied. Moreover the few studies on mental rotation ability in dementia have used two-dimensional stimuli. The goal of our research is to study the performances of subjects with neurodegenerative pathology in mental rotation tasks with two-dimensional and three-dimensional stimuli. Methods. Thirty patients with mild Alzheimer's disease (AD) and thirty elderly subjects (normal control - NC) were assessed using the Mini-Mental State Examination (MMSE), a standardized neuropsychological test and two experimental tasks developed ad hoc. The first experimental task is the "Unusual Pictures" that use two-dimensional stimuli (pictures) and is the adaptation of the test of Warrington and Taylor (1973); the second experimental task is "Spatial Rotation" that use the three-dimensional stimuli (modeling) and inspired to works of Butter et al. (1970). Results. For statistic analysis we adopted an α level of 0.05 for every analysis. In order to test the difference among groups and between tasks, transformed data were submitted to a 2x3 Analysis of variance for repeated measure, with two factors (groups) and three treatments (experimental tasks: usual and unusual vision and spatial rotation). Result showed differences between groups (p<0.001) and between tasks (p<0.001), and the presence of interaction groups by tasks (p<0.001). Post hoc analysis showed a significant different between AD and NC in tasks using both two-dimensional and three-dimensional stimuli but there isn't a difference between two groups in performances of tasks that not use the manipulation of stimuli. Conclusion. Our conclusions are that in the early stage the subjects with AD is already present a visuospatial deficit but this does not depend by stimuli used but depend on the task. It's clear that the use of ability of mental rotation is very difficult for subject with early cortical damage even in tasks that use the three-dimensional stimuli that require a lower abstraction.