Figure 5

Phase shifts of onsets of aMT6s rhythm. A. Time shifts in aMT6s onsets are contrasted in young and older groups. The abscissa represents the time of bright light stimuli (midpoint of 3 h pulse) in reference to the time of the aMT6s onset at baseline. Trend lines for each age group represent 5-point moving averages. Relative to baseline aMT6s onsets, the inflection from delays to advances occurred earlier in the older adults. B. The shifts in aMT6s onsets were averaged to show the mean ± 1 SEM shift in onset times for non-overlapping bins of time-of-stimulation referenced to aMT6s onset. The abscissa (Circadian Clock Time) is our best estimate of the mean clock time at which bright light stimuli occurred, adjusted for each participant's aMT6s onset time. Asterisks represent the mean onsets for young and older groups.