Alzheimer's disease is an insidious affliction which cripples the cognitive capabilities Of its victims. While memory complaints are the hallmark of the illness, perceptual disorders also are prevalent. Recent neuropathological and psychophysical research has demonstrated that there is a profound disturbance in the spatial temporal processing of visual stimuli. The evidence suggests that the visual experience of the Alzheimer patient is very different from that of healthy, elderly adults. it is the hypothesis of this proposal that the altered perceptual experiences can have a severe impact on a wide range of perceptual and cognitive functions. The major objective of the research project is to examine the hypothesis that Alzheimer's disease (AD) patients experience a visual disturbance which has a significant impact on higher order information processing. The objective will be explored through four specific aims using the tools of visual psychophysics, image engineering technology, and ocular neuropathology.
The first aim i s to develop a short test of spatial temporal contrast sensitivity that can be used in clinical settings. The development of the contrast sensitivity test will make this important tool available to investigators and clinicians for the evaluation of clinical populations.
The second aim i s to assess the temporal integration capabilities of AD patients with a test of motion detection. This assessment will document the degree of motion processing impairment related to dementia level, contrast sensitivity, and the gender of the patient. The contrast sensitivity and motion detection tests are noninvasive tools for the determination of specific visual system deficits. Building on the knowledge acquired in the first parts of the project regarding the capabilities of AD patients to process threshold contrast stimuli, the third aim is to examine the impact of stimulus contrast on picture naming, word learning, and face recognition tasks.
The fourth aim i s to determine the specific nature and degree of ocular neuropathology in the retinae of AD patients. This work will address directly the hypothesis that AD involves a primary visual deficit. The major outcomes of the project will be (1) the establishment of a short computer based test for the assessment of spatial temporal contrast sensitivity, (2) the characterization of the motion detection capabilities of AD patients, (3) the creation of visually fair tests for the neuropsychological testing of AD patients in tasks with a major visual component, and (4) the documentation of retinal pathology in a large number of AD patients.
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