Abstract
In the study of Alzheimer's disease, a multidisciplinary research approach has identified significant abnormality in several areas of visual and visual attention-related brain function in addition to those typically measured as part of clinical diagnosis. This raises the possibility that a similar approach applied to amnestic mild cognitive impairment (aMCI) will increase our understanding of its theoretical and clinical constructs, particularly if functions whose integrity is heterogeneous with respect to etiological outcome can be found. In this study we examined visual search performance (the brain's ability to search effectively throughout the environment for a particular object) in aMCI compared to healthy aging. Cross-sectionally, visual search performance in aMCI was significantly poorer than in healthy aging, with greater intra-group performance heterogeneity in the aMCI compared to the healthy older adult group. This outcome illustrates that although individuals within an aMCI group ostensibly have the same condition they can differ substantially with respect to the integrity of aspects of brain function. Such findings may have implications for the clinical management of the individual patient. The results from the longitudinal aspect of this study also illustrate how heterogeneity in the performance of brain operations other than memory in aMCI may help to inform the likelihood of their developing dementia, as those patients who were diagnosed with dementia within 2.5 years of baseline measurement showed significantly poorer visual search performance compared to those who did not.