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Zhong-Lin Lu, James Neuse, Stephen A. Madigan, Barbara A. Dosher; Fast Decay of Iconic Memory in Observers At-Risk for Alzheimer's Disease. Journal of Vision 2004;4(8):767. doi: 10.1167/4.8.767.
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© ARVO (1962-2015); The Authors (2016-present)
Yang (Dissertation, NYU, 1999) reported an unusual observer who showed very fast decay of iconic memory. Unexpectedly, this observer was diagnosed two years later with Alzheimer's disease. Is fast decay of the partial-report superiority effect an early sign of Alzheimer's disease? Mild Alzheimer's patients generally have significant long-term episodic and semantic memory deficits as well as deficits in working memory tasks, even though they are at most slightly impaired compared to normals in auditory and spatial short-term memory tasks. No systematic study of partial report superiority has been carried out in the Alzheimer's population. In this study, we assessed iconic memory using the partial report paradigm (Sperling, 1960) in three groups: people at-risk for Alzheimer's disease (CDR: 0.5 to 1.0), college-age young controls, and older controls. In addition, we assessed cognitive performance of the at-risk and old control groups with a neuropsychological test battery. We found (1) The at-risk observers performed significantly more poorly in a number of neuropsychological tests; (2) In pre- and simultaneous cue conditions, both the at-risk and the older control groups performed above 90% correct with no significant difference between the two, suggesting adequate and equivalent visual letter identification; (3) Neither the capacity of iconic memory nor the capacity of short-term memory was significantly correlated with age or CDR, suggesting constant iconic and short-term memory capacity over age and CDR; (4) The duration of iconic memory was very short (< 50 ms) for the at-risk observers compared to normal adults (270 ms). This difference remained significant after age was partialled out. We discuss our results in light of recent physiological studies of the locus of sensory memory and theories on aging and Alzheimer's disease.
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