title: Practice effects in healthy adults: a longitudinal study on frequent repetitive cognitive testing.
abstract: BACKGROUND
  Cognitive deterioration is a core symptom of many neuropsychiatric disorders and target of increasing significance for novel treatment strategies. Hence, its reliable capture in long-term follow-up studies is prerequisite for recording the natural course of diseases and for estimating potential benefits of therapeutic interventions. Since repeated neuropsychological testing is required for respective longitudinal study designs, occurrence, time pattern and magnitude of practice effects on cognition have to be understood first under healthy good-performance conditions to enable design optimization and result interpretation in disease trials.
  
  
  METHODS
  Healthy adults (N = 36; 47.3 ± 12.0 years; mean IQ 127.0 ± 14.1; 58% males) completed 7 testing sessions, distributed asymmetrically from high to low frequency, over 1 year (baseline, weeks 2-3, 6, 9, months 3, 6, 12). The neuropsychological test battery covered 6 major cognitive domains by several well-established tests each.
  
  
  RESULTS
  Most tests exhibited a similar pattern upon repetition: (1) Clinically relevant practice effects during high-frequency testing until month 3 (Cohen's d 0.36-1.19), most pronounced early on, and (2) a performance plateau thereafter upon low-frequency testing. Few tests were non-susceptible to practice or limited by ceiling effects. Influence of confounding variables (age, IQ, personality) was minor.
  
  
  CONCLUSIONS
  Practice effects are prominent particularly in the early phase of high-frequency repetitive cognitive testing of healthy well-performing subjects. An optimal combination and timing of tests, as extractable from this study, will aid in controlling their impact. Moreover, normative data for serial testing may now be collected to assess normal learning curves as important comparative readout of pathological cognitive processes.
authors.affiliation: Division of Clinical Neuroscience, Max Planck Institute of Experimental Medicine, Göttingen, Germany. bartels@em.mpg.de
authors.forename: Claudia
authors.initials: C
authors.lastname: Bartels
authors.forename: Martin
authors.initials: M
authors.lastname: Wegrzyn
authors.forename: Anne
authors.initials: A
authors.lastname: Wiedl
authors.forename: Verena
authors.initials: V
authors.lastname: Ackermann
authors.forename: Hannelore
authors.initials: H
authors.lastname: Ehrenreich
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000523:psychology*; D001288:Attention / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D056344:Executive Function / Q000502:physiology; D005260:Female; D006801:Humans; D007360:Intelligence; D007858:Learning / Q000502:physiology; D008137:Longitudinal Studies; D008297:Male; D008568:Memory / Q000502:physiology; D001523:Mental Disorders / Q000523:psychology; D008875:Middle Aged; D009048:Motor Skills / Q000502:physiology; D009483:Neuropsychological Tests; D010551:Personality; D011214:Practice, Psychological; D011788:Quality of Life; D012016:Reference Values; D013028:Space Perception / Q000502:physiology; D014796:Visual Perception / Q000502:physiology; D055815:Young Adult