Effects of Visual Signal Strength on Alzheimer Cognition

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DESCRIPTION (provided by applicant): Identification of factors that keep individuals with Alzheimer's disease (AD) from functioning optimally in their daily lives is of singular importance. Most aspects of visual cognition are impaired in AD, including the abilities to recognize and discriminate objects, faces, and patterns. The inability to recognize the face of a loved one or the danger in inappropriately identifying an object are some of the most devastating features of AD for both the patient and the caregiver. These visual deficits arise from pathological changes in highorder association areas of the brain but also from defective input from lower-level visual processing areas. Impairments in basic vision are prevalent in AD and can strongly predict deficits in visual cognition. We plan to apply our knowledge of the cognitive consequences of visual dysfunction in AD to designing visual-system manipulations with the goal of ameliorating cognitive deficits in this disorder. These results will indicate which cognitive and memory domains are most accessible to visual interventions and allow us to develop a visually-fair neuropsychological test battery for clinical and research use. This work continues our dual-site study with the Alzheimer Disease Centers of Boston and Cleveland. Key features of the new study are its focus on the effect of contrast manipulation on memory, and the expansion of examined levels of visual processing "downward" to include retinal change and "upward" to include the relation of visual abilities to daily activities assessed under naturalistic conditions. Another point of expansion is in the examination of nondemented individuals with Parkinson's disease (PD). Our Specific Aims are: (1) To perform experimental manipulations of contrast sensitivity and to document changes in memory and cognition as a function of normal aging, AD and PD. (2) To examine retinal and optic nerve function with frequency-doubling technology and optical coherence tomography and relate findings to visual cognition, memory, and daily activities. (3) To assess motion detection with the goal of establishing which factors are most salient to performance. (4) To relate visual abilities to daily function, as assessed by naturalistic tasks and by successful engagement in vision-dependent leisure activities and instrumental activities of daily living. Using innovative techniques, our findings will span the multiple levels of retina, basic vision, visual cognition, visual memory, and daily function, and we will attain new and more comprehensive insights into improving the quality of life of normal elderly adults and those with AD and PD.