title: Motor timing intraindividual variability in amnestic mild cognitive impairment and cognitively intact elders at genetic risk for Alzheimer's disease.
abstract: BACKGROUND
  Intraindividual variability (IIV) in motor performance has been shown to predict future cognitive decline. The apolipoprotein E-epsilon 4 (APOE-ε4) allele is also a well-established risk factor for memory decline. Here, we present novel findings examining the influence of the APOE-ε4 allele on the performance of asymptomatic healthy elders in comparison to individuals with amnestic MCI (aMCI) on a fine motor synchronization, paced finger-tapping task (PFTT).
  
  
  METHODS
  Two Alzheimer's disease (AD) risk groups, individuals with aMCI (n = 24) and cognitively intact APOE-ε4 carriers (n = 41), and a control group consisting of cognitively intact APOE-ε4 noncarriers (n = 65) completed the Rey Auditory Verbal Learning Test and the PFTT, which requires index finger tapping in synchrony with a visual stimulus (interstimulus interval = 333 ms).
  
  
  RESULTS
  Motor timing IIV, as reflected by the standard deviation of the intertap interval (ITI), was greater in the aMCI group than in the two groups of cognitively intact elders; in contrast, all three groups had statistically equivalent mean ITI. No significant IIV differences were observed between the asymptomatic APOE-ε4 carriers and noncarriers. Poorer episodic memory performance was associated with greater IIV, particularly in the aMCI group.
  
  
  CONCLUSIONS
  Results suggest that increased IIV on a fine motor synchronization task is apparent in aMCI. This IIV measure was not sensitive in discriminating older asymptomatic individuals at genetic risk for AD from those without such a genetic risk. In contrast, episodic memory performance, a well-established predictor of cognitive decline in preclinical AD, was able to distinguish between the two cognitively intact groups based on genetic risk.
authors.affiliation: a Department of Psychology , Rosalind Franklin University of Medicine and Science , North Chicago , IL , USA.
authors.forename: Christina D
authors.initials: CD
authors.lastname: Kay
authors.affiliation: a Department of Psychology , Rosalind Franklin University of Medicine and Science , North Chicago , IL , USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Seidenberg
authors.affiliation: b Department of Neurology and the Center for Imaging Research , Medical College of Wisconsin , Milwaukee , WI , USA.
authors.forename: Sally
authors.initials: S
authors.lastname: Durgerian
authors.affiliation: b Department of Neurology and the Center for Imaging Research , Medical College of Wisconsin , Milwaukee , WI , USA.|c Department of Psychology , Marquette University , Milwaukee , WI , USA.
authors.forename: Kristy A
authors.initials: KA
authors.lastname: Nielson
authors.affiliation: d Department of Kinesiology , University of Maryland , College Park , MD , USA.
authors.forename: J Carson
authors.initials: JC
authors.lastname: Smith
authors.affiliation: e Department of Psychology , Wayne State University , Detroit , MI , USA.
authors.forename: John L
authors.identifier: http://orcid.org/0000-0001-9196-3336
authors.initials: JL
authors.lastname: Woodard
authors.affiliation: f Neurological Institute , Cleveland Clinic , Cleveland , OH , USA.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Rao
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000235:genetics / Q000523:psychology; D000647:Amnesia / Q000235:genetics / Q000523:psychology*; D053327:Apolipoprotein E4 / Q000235:genetics*; D060825:Cognitive Dysfunction / Q000235:genetics / Q000523:psychology*; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D009483:Neuropsychological Tests; D012307:Risk Factors
chemical_list: D053327:Apolipoprotein E4
keywords: Aging; apolipoprotein ε4; episodic memory; intraindividual variability; mild cognitive impairment; motor timing