C. M. R. performed the statistical analyses. R. H. M. contributed to the PIB studies. D. M. managed the PIB. database. J. C. M. oversaw the clinical studies, performed some of the clinical evaluations, assisted in data evaluation and interpretation, provided critical comments during the writing of the paper and obtained funding. D. M. H. performed some of the LPs, assisted in data evaluation and interpretation, provided critical com- ments during the writing of the paper and obtained funding. Acknowledgements We gratefully acknowledge the contributions of Ms S. Sathyan, Dr J. Christiansen, Dr R. Perrin and Dr J. Ladenson, our lumbar puncture physicians, and the Clinical, Psychometrics, Imaging and Biostatistics Cores of the Washington University Alzheimer’s Disease Research Center. Supported by grants: P50 AG05681 (J. C. M.), P01 AG03991 (J. C. M.), P01 AG026276 (J. C. M.) and P30 NS057105 (D. M. H.) from the National Institute of Aging of the National Institutes of Health; P30 NS048056 (M. A. M.) from the National Institute of Neurologi- cal Disorders and Stroke; UL1 RR024992, National Center for Research Resources, NIH Roadmap for Medical Research (M. A. M.), the Dana Foundation (M. A. M.) and the Charles and Joanne Knight Alzheimer Research Initiative (J. C. M.). The authors declare that they have no conflict of interest. For more information Alzheimer’s Association http://www.alz.org/index.asp Alzheimer’s Disease Research Center at Washington University School of Medicine http://alzheimer.wustl.edu/ Alzheimer Research Forum http://www.alzforum.org/ Alzheimer’s Disease Education and Referral Center http://www.nia.nih.gov/Alzheimers/ References Aizenstein H, Nebes R, Saxton J, Price J, Mathis C, Tsopelas N, Ziolko S, James J, Snitz B, Houck P et al (2008) Frequent amyloid deposition without signiﬁcant cognitive impairment among the elderly. 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