Figure 1
Daysimeter and functional block diagram.
Figure 2
Spectral response graph. Spectral response functions generated from the model of human circadian phototransduction by Rea et al. [22]. The dashed line represents the predicted spectral response function for an equal energy spectrum light source. The continuous line represents the predicted spectral responses to individual, narrow-band light sources. The two sets of symbols represent empirical spectral response data from two independent laboratories [34, 35].
Figure 3
Logistic transfer function graph. Logistic transfer function relating nocturnal melatonin suppression to the rectified circadian light stimulus (CS) from the model of human circadian phototransduction by Rea et al. [22]. Data from several studies using both narrow-band [34, 35] and polychromatic light sources [36–38] to induce nocturnal melatonin suppression were plotted as a function of CS. A logistic function from Zeitzer et al. [23] was used to fit the data yielding a regression coefficient (r2) for the transfer function equal to 0.82. Figure was adapted from Rea et al. [22].
Figure 4
Activity and light exposure graphs: Nurses. Activity and light exposure data plotted as a function of elapsed number of days for a day-shift nurse (4a, 4c) and for a rotating-shift nurse (4b, 4d). Data collection started at a different clock time for each subject, so each "day" is a different 24-hour period of time for each subject. Circadian light stimulus (CS) exposures were measured with the Daysimeter [20], and transformed to range between the limits of human melatonin suppression (CS Logistic) shown in Figure 3.
Figure 5
Activity and light exposure graphs: Rats. Activity and light exposure data plotted as a function of elapsed time (days) for a 12L:12D rat (5a, 5c) and for a "jet lagged" rat (5b, 5d). At the start of the experiment, the photoperiods were in phase. In the first two days of the experiment, the photoperiods for both groups were the same. Wheel-running data were not collected until the third day of the study, by which time the photoperiod for the "jet-lagged" group had reversed. Most of the activity in the "jet-lagged" group on that day occurred during the light phase.
Figure 6
Behavioral entrainment-correlation functions. Behavioral entrainment-correlation functions relating activity and light exposures for two example nurses, one day-shift nurse (Figure 6a) and one rotating-shift nurse (6b) and two example rats, a rat exposed to a regular 12L:12D pattern of light and dark (6c) and a "jet-lagged" rat exposed to a 12:12 light-dark cycle that was phase-reversed every 48 hours (6d).
Figure 7
Phasor diagrams for day-shift and rotating-shift nurses and for 12L:12D and "jet-lagged" nocturnal rats.
Figure 8
Mean phasors for nurses and for rats.
Figure 9
Phasor magnitudes for the day-shift, and rotating-shift nurses (a) and for the two groups of rats (b).
Figure 10
Interdaily stability (IS) statistics for the day-shift and rotating-shift nurses (a) and for the two groups of rats (b).