Phase Shifts and Phase Response Curves

The circadian clock is not equally sensitive to a given zeitgeber at all times of day. This fact is a conserved feature in all examined taxa and is graphically summarized in a phase response curve (PRC), shown in Fig. 3, which plots the magnitude and direction of a phase shift as a function of the circadian phase at which a stimulus is applied. The PRC models the mechanisms by which the circadian clock is entrained to environmental cycles. For example, PRCs to light stimuli illustrate the differential effects of light at different circadian phases. Light, the principal environmental zeitgeber, has its greatest effect on the circadian clock when delivered during the subjective night, the time when a species is normally exposed to darkness. Light pulses will phase-delay rhythms in the early subjective night and phase-advance rhythms in the late subjective night. Little phase shifting occurs during the subjective day—the dead zone. These

Breaking Bulimia

Breaking Bulimia

We have all been there: turning to the refrigerator if feeling lonely or bored or indulging in seconds or thirds if strained. But if you suffer from bulimia, the from time to time urge to overeat is more like an obsession.

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