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Ida L. Kellison, Matthew Rizzo, Shaun P. Vecera; Visual short-term memory deficits in Alzheimer's disease. Journal of Vision 2004;4(8):770. doi: 10.1167/4.8.770.
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Objective: Research has suggested that spatial attention is impaired in Alzheimer's disease (AD) patients (Balota & Faust, 2001). We hypothesized that impairments in visual short-term memory (VSTM) produce attentional deficits in early AD. We predicted that patients with AD store fewer objects in VSTM than controls. Methods: 12 neurologically normal controls and 8 patients with mild AD performed a change detection task. A memory array of 1–4 colored squares appeared for 200 ms, followed by a 900 ms retention interval. A test array followed and contained the same number of objects shown in the memory array, with a probe box around one of the objects. Participants reported if the probed object was the same or different as in the memory array. Results: Both controls and patients performed accurately at set size 1 (99.5% controls; 96.5% patients). Patients' performance declined more dramatically than controls as set size increased (p < .0001), and the AD patients retained an average of 1.2 items in VSTM, whereas controls retained an average of 2.44 items (p < .0001). Conclusions: Controls and AD patients differ in their ability to store objects in VSTM, with patients showing a greater memory decline than older controls and a smaller VSTM capacity than older controls. These results are not due to verbal recoding; similar results are obtained when participants performed an articulatory suppression task and the VSTM task. Our results indicate that VSTM declines in early AD, possibly contributing to the decline in other high-level visual processes, such as attention.
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