Motor timing intraindividual variability in amnestic mild cognitive impairment and cognitively intact elders at genetic risk for Alzheimer's disease.
INTRODUCTION
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).


METHOD
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.
['Kay|Christina D|CD|', 'Seidenberg|Michael|M|', 'Durgerian|Sally|S|', 'Nielson|Kristy A|KA|', 'Smith|J Carson|JC|', 'Woodard|John L|JL|http://orcid.org/0000-0001-9196-3336', 'Rao|Stephen M|SM|']
D000368:Aged D000369:Aged, 80 and over D000544:Alzheimer Disease D000647:Amnesia D053327:Apolipoprotein E4 D060825:Cognitive Dysfunction D005260:Female D006801:Humans D007206:Individuality D008297:Male D009483:Neuropsychological Tests D012307:Risk Factors
motor timing intraindividual variability mild cognitive impairment episodic memory Aging apolipoprotein ε4