Alterations of visual search strategy in Alzheimer's disease and aging

Visual search, characterized by eye fixation patterns, was examined in 8 pa tients with Alzheimer's disease (AD), 8 cognitively intact, age-matched ind ividuals, and 8 young control participants as they searched for a number am ong a nonlinear array of letters on a large computer screen. Among the 3 gr oups, target detection accuracy differed and detection time increased linea rly. There were more fixations, and fixation duration was significantly lon ger in the AD patients than in the other 2 groups. These factors contribute d to the lengthening of target detection time. This qualitative difference in the architecture of visual search between AD and aging may reflect a spe cific deficit in the disengagement of visual spatial attention, a prolongat ion of saccade initiation, or inefficiency in planning a search strategy.