Fig. 3.

Scaling exponent α in all groups obtained from the detrended fluctuation analysis. Because there was no break point in the log–log plot in young control subjects, α was obtained in this group by fitting the detrended fluctuation function F(n) at time scales between 5 min and 8 h. Because of the break-point in the other groups, α was obtained between 90 min and 8 h. α = 0.50 indicates “white noise” or the scaling exponent in activity of experimental animals in the absence of the SCN influence (dashed line) (2). Error bars indicate standard error of the mean. Compared to young controls, the elderly control and very old control subjects had smaller α values, as indicated by *, P < 0.05. Elderly control and very old control subjects showed no significant difference. Early-stage AD subjects and age- and living condition-matched elderly controls showed no significant difference. Late-stage AD subjects have significantly smaller α than the age- and living condition-matched very old controls, as indicated by # (P < 0.05).