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Abstract:
Abstract: Our goal was to evaluate object perception,
visuospatial perception and visuomotor control in Alzheimer's
Disease (AD) patients. To our knowledge this is the first study to
examine all three higher visual behaviors within the same AD
patients. Twelve early stage probable AD patients and 11 matched
control subjects participated. Object perception was evaluated
using a face matching task and a shape discrimination task for
pairs of visually similar objects. Visuospatial perception was
examined by measuring the accuracy with which subjects copied
configurations of spatial arrays containing five circular tokens.
Visuomotor control was evaluated by measuring the accuracy with
which subjects placed their fingers on the circumference of
irregularly shaped objects when reaching and grasping them. AD
patients performed significantly below controls on face matching,
on difficult shape discriminations where the object pair was
identical but differed in orientation, and in absolute accuracy on
copies of spatial arrays. AD visuomotor grasping accuracy was
equivalent to controls. In conclusion, higher visual abilities are
differentially affected in mild AD. Visuomotor behavior remains
intact in the presence of compromised object perception and, to a
slightly lesser extent, space perception. Our results are
consistent with the proposal that visual perception and visual
motor control rely on distinct neural substrates.
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