title: Working memory binding and episodic memory formation in aging, mild cognitive impairment, and Alzheimer's dementia.
abstract: BACKGROUND
  Recent studies indicate that in both normal and pathological aging working memory (WM) performance deteriorates, especially when associations have to be maintained. However, most studies typically do not assess the relationship between WM and episodic memory formation. In the present study, we examined WM and episodic memory formation in normal aging and in patients with early Alzheimer's disease (mild cognitive impairment, MCI; and Alzheimer's dementia, AD).
  
  
  METHODS
  In the first study, 26 young adults (mean age 29.6 years) were compared to 18 middle-aged adults (mean age 52.2 years) and 25 older adults (mean age 72.8 years). We used an associative delayed-match-to-sample WM task, which requires participants to maintain two pairs of faces and houses presented on a computer screen for short (3 s) or long (6 s) maintenance intervals. After the WM task, an unexpected subsequent associative memory task was administered (two-alternative forced choice). In the second study, 27 patients with AD and 19 patients with MCI were compared to 25 older controls, using the same paradigm as that in Experiment 1.
  
  
  RESULTS
  Older adults performed worse than both middle-aged and young adults. No effect of delay was observed in the healthy adults, and pairs that were processed during long maintenance intervals were not better remembered in the subsequent memory task. In the MCI and AD patients, longer maintenance intervals hampered the task performance. Also, both patient groups performed significantly worse than controls on the episodic memory task as well as the associative WM task.
  
  
  CONCLUSIONS
  Aging and AD present with a decline in WM binding, a finding that extends similar results in episodic memory. Longer delays in the WM task did not affect episodic memory formation. We conclude that WM deficits are found when WM capacity is exceeded, which may occur during associative processing.
authors.affiliation: a Donders Institute for Brain, Cognition and Behaviour, Radboud University , Nijmegen , The Netherlands.
authors.forename: Bonnie
authors.initials: B
authors.lastname: van Geldorp
authors.forename: Sophie M
authors.initials: SM
authors.lastname: Heringa
authors.forename: Esther
authors.initials: E
authors.lastname: van den Berg
authors.forename: Marcel G M
authors.initials: MG
authors.lastname: Olde Rikkert
authors.forename: Geert Jan
authors.initials: GJ
authors.lastname: Biessels
authors.forename: Roy P C
authors.initials: RP
authors.lastname: Kessels
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D000544:Alzheimer Disease / Q000150:complications*; D000704:Analysis of Variance; D060825:Cognitive Dysfunction / Q000150:complications*; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology*; D061212:Memory, Episodic; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D014706:Verbal Learning / Q000502:physiology
keywords: Aging; Alzheimer’s disease; Binding; Episodic memory; Relational memory; Working memory