Characteristics of visual target influence detection of change in naturalistic scenes in Alzheimer disease

Objective: To examine the role of visual characteristics of the target on Alzheimer disease (AD) patients\u27 ability to detect change in naturalistic scenes. Background: AD patients exhibit impairments in detecting changes in the visual environment. Unexamined to date is the influence of visual characteristics of the target on this ability. Method: The change-detection experiment used 36 pairs of photographs of naturalistic scenes. Each pair was identical except for one target that differed in color, gray-scale, or presence/absence. Scene complexity also varied. The task was to locate the target; reaction times (RTs) were recorded. Results: RTs increased as scene complexity increased. AD patients exhibited slower RTs than elderly adult controls (ECs), who were slower than young adults (N=14/group). AD patients were unable to locate the target in 33.3% to 61.9% of the complex gray-scale trials, compared with 4.8% to 38.1% in the EC group. Performance on color and presence/absence trials was relatively good for all groups. Conclusions: The ability of AD patients to detect change in simulated real-world scenes is influenced by visual characteristics of the target and by scene complexity