Circadian phase resetting by a single short-duration light exposure

Abstract

IntroductionLight is the strongest environmental time cue for resetting the circadian clock in mammals, including humans (1, 2). Initial studies examining the phase-resetting effects of light used long-duration (5 hours) and high-intensity (~9,500 lux) light (2) because the human circadian system was thought to be less sensitive to light than that of other mammals. While the circadian pacemaker in mice (3), rats (4), hamsters (5), and humans (6, 7) is known to respond to a sequence of millisecond flashes (administered over 5 seconds in rats, over 5-60 minutes in mice and hamsters, and over 60 minutes in humans), a single millisecond flash does not reset the mammalian pacemaker at the intensities that have been tested (3,8), suggesting that circadian resetting requires integration of the photic signal over a longer exposure interval.A nonlinear relationship exists between light exposure (LE) duration and the magnitude of circadian phase resetting responses. A single 12-minute pulse of light can shift the human pacemaker 8 times more BACKGROUND. In humans, a single light exposure of 12 minutes and multiple-millisecond light exposures can shift the phase of the circadian pacemaker. We investigated the response of the human circadian pacemaker to a single 15-second or 2-minute light pulse administered during the biological night.

Human circadian phase–response curves for exercise

“…Further human dose-response studies manipulating both intensity and duration of exercise will be needed to address the practicality and efficacy of using exercise to shift the circadian system. Although very short bright light pulses have shifted circadian rhythms under extreme laboratory conditions (e.g., continuous bedrest) (Rahman et al, 2017), potential circadian phase-resetting by short duration and high intensity exercise has not been tested.…”

Precision Light for the Treatment of Psychiatric Disorders

“…It was intuitive to many that, if the human circadian system was not privileged, then it certainly was not as photosensitive as the systems studied in lower organisms such as fungi and Drosophila [ 39 ]. Along with the circadian flash literature, recent work continues to refute these beliefs (see [ 183 ] for a description of human resetting with a single 15 s light exposure). The fact that people are responsive to millisecond introductions of light has important implications for psychiatry.…”

An Exploration of the Temporal Dynamics of Circadian Resetting Responses to Short- and Long-Duration Light Exposures: Cross-Species Consistencies and Differences

“…An essential feature of the Figure 1B presentation is that the two curves do not intersect. Although prior discussions of the data in Figure 1B have modeled the dynamics using a single four-parameter logistic function (Chang et al, 2012;Rahman et al, 2017), in the leaky integrator analysis formulated below, we propose to embrace these disparate behaviors as limiting cases of a single first-order dynamical system defined by a time constant, B −1 , as an alternative model. Before we can develop the leaky integrator model, however, we need to address a fundamental question that we deferred to this section: in defining the long-T linear incremental function, may we use all 4 data points, T ≥ 60 minutes, or should we restrict the range to the 3 data points T > 60 minutes (corresponding to T ≥ 150 minutes in our data set)?…”

“…The phase of the mammalian circadian pacemaker can be shifted by environmental light. The size of the phase shift depends on the wavelength, intensity, duration, and timing of the light stimulus (Zeitzer et al, 2000;Khalsa et al, 2003;Lockley et al, 2003;Gooley et al, 2010;Chang et al, 2012;St Hilaire et al, 2012;Rüger et al, 2013;Rahman et al, 2017); Nelson and Takahashi, 1991;Comas et al, 2006;Dkhissi-Benyahya et al, 2007;Czeisler, 1995;Czeisler and Gooley, 2007). These responses have been extensively studied in both nocturnal and diurnal mammals, including humans.…”