TY - JOUR
T1 - Reduction of scale invariance of activity fluctuations with aging and Alzheimer's disease
T2 - Involvement of the circadian pacemaker
AU - Hu, Kun
AU - Van Someren, Eus J.W.
AU - Shea, Steven A.
AU - Scheer, Frank A.J.L.
PY - 2009/2/24
Y1 - 2009/2/24
N2 - Human motor control systems orchestrate complex scale-invariant patterns of activity over a wide range of time scales (minutes to hours). The neural mechanisms underlying scale-invariance are unknown in humans. In rats, the master circadian pacemaker [suprachiasmatic nucleus (SCN)] is crucially involved in scale- invariant activity fluctuations over multiple time scales from minutes to 24 h. Aging and Alzheimer's disease (AD) are associated with progressive dysfunction of the SCN. Thus, if the SCN is responsible for the scale-invariant activity fluctuations in humans, we predict disturbances of scale-invariant activity fluctuations in elderly humans and even more pronounced disturbances in elderly humans with AD. To test these hypotheses, we studied spontaneous daytime activity patterns in 13 young adults (mean ± SD: 25.5 ± 6.1 y); 13 elderly people with early-stage AD (68.5 ± 6.1 y) matched with 13 elderly controls (68.6 ± 6.1 y); and 14 very old people with late-stage AD (83.9 ± 6.7 y) matched with 12 very old controls (80.8 ± 8.6 y). In young adults, activity exhibited robust scale-invariant correlations across all tested time scales (minutes to 8 h). The scale-invariant correlations at 1.5-8 h declined with age (P = 0.01) and were significantly reduced in the elderly (P = 0.04) and very old controls (P = 0.02). Remarkably, an age-independent AD effect further reduced the scale-invariant correlations at 1.5-8 h(P = 0.04), leading to the greatest reduction of the scale-invariant correlations in very old people with late-stage AD-resembling closely the loss of correlations at large time scales in SCN-lesioned animals. Thus, aging and AD significantly attenuate the scale invariance of activity fluctuations over multiple time scales. This attenuation may reflect functional changes of the SCN.
AB - Human motor control systems orchestrate complex scale-invariant patterns of activity over a wide range of time scales (minutes to hours). The neural mechanisms underlying scale-invariance are unknown in humans. In rats, the master circadian pacemaker [suprachiasmatic nucleus (SCN)] is crucially involved in scale- invariant activity fluctuations over multiple time scales from minutes to 24 h. Aging and Alzheimer's disease (AD) are associated with progressive dysfunction of the SCN. Thus, if the SCN is responsible for the scale-invariant activity fluctuations in humans, we predict disturbances of scale-invariant activity fluctuations in elderly humans and even more pronounced disturbances in elderly humans with AD. To test these hypotheses, we studied spontaneous daytime activity patterns in 13 young adults (mean ± SD: 25.5 ± 6.1 y); 13 elderly people with early-stage AD (68.5 ± 6.1 y) matched with 13 elderly controls (68.6 ± 6.1 y); and 14 very old people with late-stage AD (83.9 ± 6.7 y) matched with 12 very old controls (80.8 ± 8.6 y). In young adults, activity exhibited robust scale-invariant correlations across all tested time scales (minutes to 8 h). The scale-invariant correlations at 1.5-8 h declined with age (P = 0.01) and were significantly reduced in the elderly (P = 0.04) and very old controls (P = 0.02). Remarkably, an age-independent AD effect further reduced the scale-invariant correlations at 1.5-8 h(P = 0.04), leading to the greatest reduction of the scale-invariant correlations in very old people with late-stage AD-resembling closely the loss of correlations at large time scales in SCN-lesioned animals. Thus, aging and AD significantly attenuate the scale invariance of activity fluctuations over multiple time scales. This attenuation may reflect functional changes of the SCN.
KW - Actigraphy
KW - Fractal
KW - Motor control
KW - Sleep-wake rhythm suprachiasmatic nucleus
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U2 - 10.1073/pnas.0806087106
DO - 10.1073/pnas.0806087106
M3 - Article
C2 - 19202078
AN - SCOPUS:62449216579
SN - 0027-8424
VL - 106
SP - 2490
EP - 2494
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 8
ER -