The association between visual discrimination and cognitive decline prior to clinical diagnosis

Abstract

AbstractBackgroundThe development of dependable screening methods would allow for the early detection of incipient Alzheimer's disease (AD). Alzheimer’s pathology accumulates in the perirhinal cortex (PRC) well before diagnosis. Converging lines of research show the PRC critically contributes to object visual processing, especially when disambiguating between objects that have highly overlapping features (Barense et al., 2010; Bussey et al., 2002). Previous research has shown that healthy older adults with a genetic risk (i.e., family history) for AD, performed worse at discriminating novel objects than those without a genetic risk (Mason et al., 2017). A dependable screening method, such as a visual discrimination task, could help identify cognitive decline earlier than a typical screening tool.MethodTwenty‐nine healthy older adults were tested on a visual discrimination task and were also administered the Montreal Cognitive Assessment (MoCA). Based on their MoCA scores, the participants were divided into an “at‐risk” group (n=13) and a “healthy” group (n=16). Each trial consisted of the simultaneous presentation of three visually similar images. Participants were instructed to identify the image that was inconsistent with the other two as quickly and accurately as possible. Images were divided into three categories: faces, scenes, and objects.ResultThe at‐risk group scored significantly lower on the visual discrimination task when compared to the healthy group (p = 0.004). Further, there was a significant interaction between visual image category and MoCA performance on accuracy. This interaction was due to the large difference in accuracy between the two groups in the object category (p < 0.001). Finally, the category had a significant effect on accuracy, where both groups scored significantly lower in the object category (p < 0.001).ConclusionThis study shows participants who are at‐risk for mild cognitive impairment performed significantly worse on the visual discrimination task especially in the object condition, which is consistent with previous results in healthy older adults with a genetic risk of AD. Impaired visual discrimination could reflect very early AD pathology affecting the PRC. Visual discrimination tests could be developed into dependable screening tools allowing clinicians to make earlier predictions about who is most at risk for developing AD.