We examined performance of healthy older and younger adults and individuals with Alzheimer’s disease (AD) and Parkinson’s disease (PD) on digit cancellation, a task putatively sensitive to cognitive impairment but possibly affected by visual impairment, particularly in contrast sensitivity. Critical contrast thresholds were established to create custom stimulus arrays that were proximally matched across individuals. Age- and PD-related differences in search were fully accounted for by the sensory deficit. Increased contrast benefited AD patients but could not override cognitive impairment. We conclude that visually-fair neuropsychological testing can effectively compensate for normal age- and PD-related visual changes that affect cognitive performance.

Research studies involving ascertainment of cognitive status of older people, particularly those that require periodic follow-up, such as those focusing on healthy aging, commonly suffer from lack of representativeness of subjects, often brought about by problems related to mobility of potential participants. It is also crucial that normal individuals who are recruited initially to serve as controls in epidemiologic studies of dementing illnesses be reevaluated periodically, and this may be hindered by the same obstacles. (ABSTRACT TRUNCATED)

External support may improve task performance regardless of an individual’s ability to compensate for cognitive deficits through internally-generated mechanisms. We investigated if performance of a complex, familiar visual search task (the game of bingo) could be enhanced in groups with suboptimal vision by providing external support through manipulation of task stimuli. Participants were 19 younger adults, 14 individuals with probable Alzheimer’s disease (AD), 13 AD-matched healthy adults, 17 non-demented individuals with Parkinson’s disease (PD), and 20 PD-matched healthy adults. We varied stimulus contrast, size, and visual complexity during game play. The externally-supported performance interventions of increased stimulus size and decreased complexity resulted in improvements in performance by all groups. Performance improvement through increased stimulus size and decreased complexity was demonstrated by all groups. AD also obtained benefit from increasing contrast, presumably by compensating for their contrast sensitivity deficit. The general finding of improved performance across healthy and afflicted groups suggests the value of visual support as an easy-to-apply intervention to enhance cognitive performance.