Environmental perturbations also have the capacity to disrupt synchrony and misalign this clock network ( Fekete et al., 1985 Cho et al., 2000 Devan et al., 2001 Ruby et al., 2008 Loh et al., 2010 Gibson et al., 2010 Karatsoreos et al., 2011 Fonken et al., 2012 LeGates et al., 2012 Fernandez et al., 2014) and are problematic as many people in our modern society extend their work and recreation into the night hours. Genetic disruption of these molecular oscillations has severe consequences on cognition ( Van der Zee et al., 2008 Wang et al., 2009 Wardlaw et al., 2014). This network regulates cognitive processes ( Holloway and Wansley, 1973 Chaudhury and Colwell, 2002), and the neural circuits involved in learning and memory also exhibit circadian rhythms in gene expression and synaptic plasticity ( Eckel-Mahan et al., 2008 Fropf et al., 2014 Lamont et al., 2005 Lyons, 2006). The circadian system is a finely tuned network of central and peripheral oscillators headed by a master pacemaker, the suprachiasmatic nucleus (SCN), which governs daily rhythms in physiology and behaviour, including cognition. If so, these findings will have implications for the many individuals whose mealtimes, for work or social reasons, are out of synchrony with their body clocks. therefore suggest that the misalignment of these circadian clocks impairs cognition.įurther experiments are needed to determine whether a similar relationship exists between the timing of meals and cognitive performance in humans. In particular, daytime feeding changed the timing of the secondary circadian clock within the hippocampus, although it had no effect on the master clock in the SCN. The daytime-fed mice showed changes in a region of the brain called the hippocampus, which supports learning and memory. showed that rodents that were instead fed during the day performed less well on cognitive tests than other mice who received the same food at night. Mice normally consume most of their food after sunset.
therefore decided to investigate whether eating outside normal waking hours would also affect other key physiological processes, specifically the cognitive processes of learning and memory.
However, more recent evidence suggests that the timing of meals may also affect circadian clocks, particularly those within the digestive system. These secondary clocks normally operate in synchrony with the SCN.Įxposure to light has long been known to influence circadian rhythms. However, most organs, from the heart to the pancreas, also possess their own clocks, which help to regulate organ-specific processes. Daily exposure to light keeps the SCN synchronized with the 24-hour day/night cycle. They also affect when we feel hungry, when our muscles work most efficiently, and when we are mentally at our sharpest.Ī region of the brain called the suprachiasmatic nucleus (SCN) generates and maintains circadian rhythms, and thus acts as the body’s master clock.
In addition to patterns of sleep and wakefulness, such circadian rhythms help to regulate body temperature, blood pressure and hormone levels. Many processes within the body follow an approximately 24-hour cycle.
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