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β-amyloid (Aβ) deposition is pathognomic for Alzheimer's disease (AD), but may occur in normal elderly people without apparent cognitive effect. Episodic memory impairment is an early and prominent sign of AD, but its relationship with Aβ burden in non-demented persons and in AD patients is unclear. We examined this relationship using ¹¹C-PIB-PET as a quantitative marker of Aβ burden in vivo in healthy ageing (HA), mild cognitive impairment (MCI) and AD. Thirty-one AD, 33 MCI and 32 HA participants completed neuropsychological assessment and a ¹¹C-PIB-PET brain scan. Multiple linear regression analyses were conducted relating episodic memory performance and other cognitive functions to Aβ burden. Ninety-seven percent of AD, 61% of MCI and 22% of HA cases had increased cortical PIB binding, indicating the presence of Aβ plaques. There was a strong relationship between impaired …