Visual selective attention in Alzheimer's disease: Effects of physical similarity, density, and target -to -distractor ratio in a cancellation task.
Item
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Title
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Visual selective attention in Alzheimer's disease: Effects of physical similarity, density, and target -to -distractor ratio in a cancellation task.
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Identifier
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AAI3037441
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identifier
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3037441
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Creator
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Schaefer, Lynn Anne.
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Contributor
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Adviser: Nancy S. Foldi
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Date
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2002
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Language
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English
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Publisher
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City University of New York.
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Subject
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Psychology, Psychobiology | Psychology, Clinical | Psychology, Cognitive
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Abstract
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Patients with Alzheimer's disease (AD) have deficits in visual selective attention. Two experiments examined the effects of systematically varying the physical characteristics of a cancellation task on qualitative (omission and commission errors) and quantitative (completion time) measures of performance. It was posited that higher physical demands represent increased perceptual load, and that the increased load would impair selective attentional skills in AD.;In Experiment 1, 15 AD subjects and 15 age-matched controls were administered 18 cancellation tests varying by 3 levels of physical similarity between targets and distractors (Similarity) and 3 levels of number of items per page (Density). AD subjects made more commission errors at the highest and middle levels of Similarity (p < 0.05), and took longer than controls (p = 0.06, trend) both as Similarity increased and at the highest Density level (p < 0.05). Increased commission errors and completion time at higher levels, and not at the lowest level, show that increased task load affects AD subjects.;In Experiment 2, 15 AD subjects and 15 age-matched controls were administered 15 cancellation tests varying by 3 levels of Density and 5 levels of the number of targets relative to the number of distractors (Target-to-Distractor Ratio). AD subjects made significantly more commission errors as Target-to-Distractor Ratio and Density interacted (p < 0.0001), and took longer than controls as Target-to-Distractor Ratio increased (p < 0.01). The AD subjects' greater completion time may in part reflect more time needed to cancel distractors, but may also reflect a less efficient search strategy as perceptual demands of Target-to-Distractor Ratio change. However, both groups canceled stimuli at the same rate (completion time/total cancellations).;The current findings suggest that selective attention skills in AD are intact at lower levels of perceptual load, where attentional capacity is not taxed. The selective attention deficits in AD were revealed only at high levels of perceptual load (e.g., at high levels of physical discrimination, and at the interaction between quantity and relevance of items). At these higher attentional loads, impoverished inhibitory mechanisms affected performance. These data suggest that commission errors are associated with compromised executive functioning, which contributes to the selective attention deficits in Alzheimer's disease.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
