Circadian rhythms for cognition: Notes on the biochronology of health, resilience & performance

By Mark Ashton Smith May 9, 2020

Cognitive performance and mood as well as variables of our physiology vary predictably over the daily, 24-h cycle. These rhythms are intimately linked with our cycle of sleep and wakefulness and are driven by our internal circadian clock, a biological pacemaker.

Human’s performance and most biological functions express rhythmic fluctuations across a 24-h-period: an increase during the day and a decrease at night.

Known

What we know with confidence: 

  • There is a high amplitude internal (endogenous) circadian rhythm – determined genetically – for cognitive, mood, and physiological variables:
    • Temperature
    • Cortisol

  • Circadian oscillators. Behavior and physiology are regulated by a hierarchically organized system of circadian (approx. 24 hour) oscillators located in the brain and in most peripheral tissues and organs.

Journal of Endocrinology 243, 3; 10.1530/JOE-19-0256

 

  • Circadian clock genes throughout all cells. There are circadian rhythms found in the almost all cells in the body. A considerable portion (approximately 10%) of genes expressed in cells or tissues have been found to display circadian oscillations.
  • The superchiasmatic nuclei. There is a master-clock (pacemaker/oscillator) in hypothalamus of the brain called the suprachiasmatic nuclei (SCN). The role of the SCN is to keep these local clocks in synchrony with each other and with the solar cycle through secretion of endogenous regulatory factors. Circadian cycles are determined genetically by a core set of clock genes.

hypothalamus

  • Zeitgebers. Internal circadian rhythms can be entrained/synchronized by regularly occuring cues (zeitgebers). 
    • In the SCN, the circadian clock mainly responds to the light dark cycle. 
    • In peripheral tissues,  circadian rhythms can be synchronized by food (mainly) , but also temperature. 
    • Also internal signals such as circulating hormones, cytokines, metabolites, sympathetic nervous activation (associated with activity), and body temperature are significant timing cues that regulate peripheral clocks.
  • Food  cues. The daily rhythm of food intake provides stimuli that entrain most peripheral and central oscillators. Feeding cycles can entrain the liver independently of the SCN and the light cycle. These hormones show circadian rhythms that can be entrained through feeding patterns (and are also influenced by the central SCN pacemaker).
    • Corticosterone
    • Ghrelin
    • Leptin
    • Insulin
    • Glucagon
    • Glucagon-like peptide
  • Chronotypes (chronological phenotypes). Individuals have different chronotypes. Early chronotype (EC), intermediate chronotype (IC) and late chronotype (LC).

Chronotype refers to when an individual’s endogenous circadian clock synchronises (entrains) to the 24 h day – largely due to activity patterns related to sleep cycles. The reference point to assign chronotype is based on the midpoint of sleep on free days. Chronotype depends on genetic and environmental factors but also on age (with midpoint of sleep getting earlier with age)

From: Facer-Childs & Brandstaetter (2015)

 

 

  • Interactions. The combination of the following determine the rhythms in our physiology, cognition and behaviour:
    • Internal circadian rhythms
    • External cues
    • Chronotypes
  • Circadian disruption. This occurs when the internal circadian rhythms are in conflict with each other and/or with external cues (e.g during shiftwork or irregular eating habits)

  • Disruption of the circadian rhythms can increase risk of:
    • Childhood diseases
    • Inflammatory diseases
    • Metabolic diseases
    • Neurological diseases (e.g. Alzheimers, Parkinson/s disease)
    • Mental illnesses
    • Cancer
    • Digestive system disease
    • Cardiovascular disease
    • Issues with general health & athletic performance
    • Also: impaired learning
  • Sleep-wake homeostasis. Circadian rhythms have a strong influence on sleep-wake homeostasis but they can be dissociated.

  • Health and adaptation. For optimal health and mental function you need to maintain an undisrupted circadian rhythm, in sync with external cues.
  • Eating & fasting. Your body benefits from 14 hours of fasting every day to  function properly. Eat within the same 10 hour window every day. Stop eating at least 3 hours before you go to sleep. There can be exceptions, but it’s key to have awareness.
    • glucose tolerance and insulin sensitivity (the body has a natural rhythm
    • glucose regulation 
    • weight (about 5% weight loss)
    • endurance,
    • blood pressure
  • Cognitive CR. Alertness & neurobehavioural performance (cognitive competence) varies systematically in circadian rhythms, independently of time since waking. Cognition is also sensitive to time spent awake.
  • Other conditions that may change performance during the day are a 90-minute ultradian cycle in alertness, sleepiness occurring immediately after awakening from sleep (“sleep inertia”), and a post-lunch dip in alertness.
  • Ultradian rhythms. Under basal (i.e., unstressed) conditions, glucocorticoids are released with an ultradian pattern (approx 1 per hour) that results in rapid ultradian oscillations of hormone levels both in the blood and within target tissues, including the brain. Oscillating pattern of plasma cortisol is important for maintenance of healthy brain responses including working memory.
  • Synaptic plasticity. The synaptic plasticity underlying  memory formation and maintenance (LTP in hippocampus) is not a static phenomenon but rather changes over time with the circadian cycle. It is most active in the night period of the circadian cycle.
  • Skill learning. Sleep plays a crucial role in the development of skill learning. Evidence of sleep-dependent skill learning has now been demonstrated across a wide variety of skill domains, including the visual, auditory, and motor (Smith and systems. Specifically, sleep has been implicated in the ongoing process of consolidation after initial acquisition. Both declarative and procedural memory benefit from restorative sleep. There is a slow wave sleep-dependent reactivation of cortical and hippocampal circuits that occurs in association with consolidation of memory. REM sleep may also be involved.
  • Sleep inertia. Performance is markedly degraded during the transition from wakefulness to sleep. (review: Czeisler & Gooley, 2007).
  • Chronic sleep deprivation. A number of consecutive nights of inadequate sleep have been shown to have detrimental effects on alertness, vigilance, psychomotor skills, and mood. Objective measures of performance, including reaction time and memory, worsen. Sleep deprivation is associated with decreased metabolism in the thalamus, prefrontal cortex, and parietal cortex. The amount of time it takes to react to a visual stimulus (simple reaction time) averages three times larger after 24 hours of wakefulness at an adverse circadian phase than before an individual has stayed up all night.
  • Cognition, metabolic function & temperature. Better cognitive performance is associated with higher core body temperature, that is itself a reflection of optimal metabolic function

(Cajochen et al. 1999 – 10 subjects)

    • Additional circadian rhythms in performance:
      • Discrimination. People detect changes in luminosity and sound more easily in the evening, compared with the morning.
      • Time estimates. Individuals estimate more accurately a 10-second interval during the afternoon and evening.
      • Reaction time. Best performance occurs in the evening, and worst performance occurs in the night and first hours of the morning.
      • Working memory. 80% the performance comparing 6-11pm to 5-8pm.
      • Emotional reactivity.
      • Sustained attention.
      • Selective attention
      • Speed of processing
  • The default mode network (DMN) decreases its integration in the afternoon compared to in the morning.
  • In the morning compared to the evening session, we found increased connectivity between regions which are part of visual and sensorimotor networks and the thalamus. The thalamus is a critical structure for the integration and processing of sensory and motor information.

Folkard, 1980

For learning word associations (e.g. in vocabulary):

Chronotypes

A. White – ECTs, Grey – LCT. B. Intermediate. C. Early. D Late

executive function

 


Maximum voluntary contraction From Facer-Childs et al. 2018

Athletic performance (percentage of personal best performance) – maximal oxygen uptake (cardiovascular fitness)



From Facer-Childs, E., & Brandstaetter, R. (2015)

 

References

Chaudhury, D., Wang, L. M., & Colwell, C. S. (2005). Circadian Regulation of Hippocampal Long-Term Potentiation. Journal of Biological Rhythms, 20(3), 225–236. https://doi.org/10.1177/0748730405276352

Czeisler, C. A., & Gooley, J. J. (2007). Sleep and circadian rhythms in humans. Cold Spring Harbor Symposia on Quantitative Biology, 72, 579–597. https://doi.org/10.1101/sqb.2007.72.064

Dhillon, J., Tan, S.-Y., & Mattes, R. D. (2017). Effects of almond consumption on the post-lunch dip and long-term cognitive function in energy-restricted overweight and obese adults. British Journal of Nutrition, 117(3), 395–402. https://doi.org/10.1017/S0007114516004463

Fafrowicz, M., Bohaterewicz, B., Ceglarek, A., Cichocka, M., Lewandowska, K., Sikora-Wachowicz, B., Oginska, H., Beres, A., Olszewska, J., & Marek, T. (2019). Beyond the Low Frequency Fluctuations: Morning and Evening Differences in Human Brain. Frontiers in Human Neuroscience, 13. https://doi.org/10.3389/fnhum.2019.00288

Facer-Childs, E. R., Boiling, S., & Balanos, G. M. (2018). The effects of time of day and chronotype on cognitive and physical performance in healthy volunteers. Sports Medicine – Open, 4(1), 47. https://doi.org/10.1186/s40798-018-0162-z

Facer-Childs, E., & Brandstaetter, R. (2015). The impact of circadian phenotype and time since awakening on diurnal performance in athletes. Current Biology: CB, 25(4), 518–522. https://doi.org/10.1016/j.cub.2014.12.036

Folkard, S., & Monk, T. H. (1980). Circadian rhythms in human memory. British Journal of Psychology, 71(2), 295–307. https://doi.org/10.1111/j.2044-8295.1980.tb01746.x

Kalafatakis, K., Russell, G. M., Harmer, C. J., Munafo, M. R., Marchant, N., Wilson, A., Brooks, J. C., Durant, C., Thakrar, J., Murphy, P., Thai, N. J., & Lightman, S. L. (2018). Ultradian rhythmicity of plasma cortisol is necessary for normal emotional and cognitive responses in man. Proceedings of the National Academy of Sciences, 115(17), E4091–E4100. https://doi.org/10.1073/pnas.1714239115

Kuriyama, K., Mishima, K., Suzuki, H., Aritake, S., & Uchiyama, M. (2008). Sleep Accelerates the Improvement in Working Memory Performance. Journal of Neuroscience, 28(40), 10145–10150. https://doi.org/10.1523/JNEUROSCI.2039-08.2008

Kyriacou, C. P., & Hastings, M. H. (2010). Circadian clocks: Genes, sleep, and cognition. Trends in Cognitive Sciences, 14(6), 259–267. https://doi.org/10.1016/j.tics.2010.03.007

Pay attention to your body’s master clock | Emily Manoogian |TEDxSanDiegoSalon—YouTube. (n.d.). Retrieved 5 May 2020, from https://www.youtube.com/watch?v=SrBYSinpEtU

Monk, T. H., Buysse, D. J., Reynolds, C. F., Berga, S. L., Jarrett, D. B., Begley, A. E., & Kupfer, D. J. (1997). Circadian rhythms in human performance and mood under constant conditions. Journal of Sleep Research, 6(1), 9–18. https://doi.org/10.1046/j.1365-2869.1997.00023.x

Patton, D. F., & Mistlberger, R. E. (2013). Circadian adaptations to meal timing: Neuroendocrine mechanisms. Frontiers in Neuroscience, 7. https://doi.org/10.3389/fnins.2013.00185

Qian, X., Droste, S. K., Lightman, S. L., Reul, J. M. H. M., & Linthorst, A. C. E. (2012). Circadian and ultradian rhythms of free glucocorticoid hormone are highly synchronized between the blood, the subcutaneous tissue, and the brain. Endocrinology, 153(9), 4346–4353. https://doi.org/10.1210/en.2012-1484

Roenneberg, T., Kuehnle, T., Pramstaller, P. P., Ricken, J., Havel, M., Guth, A., & Merrow, M. (2004). A marker for the end of adolescence. Current Biology, 14(24), R1038–R1039. https://doi.org/10.1016/j.cub.2004.11.039

Valdez, P., Reilly, T., & Waterhouse, J. (2008). Rhythms of Mental Performance. Mind, Brain, and Education, 2(1), 7–16. https://doi.org/10.1111/j.1751-228X.2008.00023.x

Valdez, P., Ramírez, C., & García, A. (2012, December 17). Circadian rhythms in cognitive performance: Implications for neuropsychological assessment. ChronoPhysiology and Therapy; Dove Press. https://doi.org/10.2147/CPT.S32586

van Moorsel, D., Hansen, J., Havekes, B., Scheer, F. A. J. L., Jörgensen, J. A., Hoeks, J., Schrauwen-Hinderling, V. B., Duez, H., Lefebvre, P., Schaper, N. C., Hesselink, M. K. C., Staels, B., & Schrauwen, P. (2016). Demonstration of a day-night rhythm in human skeletal muscle oxidative capacity. Molecular Metabolism, 5(8), 635–645. https://doi.org/10.1016/j.molmet.2016.06.012

Xie, Y., Tang, Q., Chen, G., Xie, M., Yu, S., Zhao, J., & Chen, L. (2019). New Insights Into the Circadian Rhythm and Its Related Diseases. Frontiers in Physiology, 10. https://doi.org/10.3389/fphys.2019.00682

 

This article was posted in Circadian Rhythms and tagged , .