Disrupting Circadian rhythms Jet Lag and Shift Lag Aims To know the symptoms of Jet Lag To understand the effects of jet lag upon biological rhythms To be able to understand the effects on the SCN of disruptions to EP and EZ co-ordination

Key concepts SCN disruption EP and EZ De-synchronisation Performance decrement One day to adjust for every hour of time change East to West is best – Phase Delay West to East is a beast – Phase Advance Melatonin treatment Fasting

The consequences of Jet Lag Jet lag When travelling to different parts of the world, for some days after the journey, The Sleep/Wake cycle is disrupted The Body temperature changes Other symptoms; – Daytime sleepiness, fatigue, – difficulty concentrating, headache, irritability, gastric discomfort, and trouble initiating and maintaining sleep. #SCN is disrupted

Jet Lag East to west is best PD Melatonin Bright light/artificial light Fasting then eat on new time schedule BASE BALL STUDY Alcohol coffee can have a cumulative effect in disruption Food can reset some biological clocks Social customs sleep when supposed to eat when supposed to

Cause We can fix the disruption by using: Melatonin Food And Bright light (phototherapy )

Task: SCN Disruption Complete the following diagram; labelling – SCN – Cannot cope with sudden changes – Dorsal – Ventral – Protein synthesis (CLK+BLMAL1) – Negative feedback loop Ventral SCN influenced by external cues (Light) Dorsal SCN less affected by light

Disrupting the SCN (s) The neurons of the ventral SCN are now believed to function not so much as clocks but rather as the location in the SCN that receives and responds to external inputs, while the neurons of the dorsal SCN are believed to constitute the SCN’s actual robust, endogenous clock. This view is supported by certain jet-lag experiments which have shown that in rats, the process by which a light stimulus resets the internal clock occurs far more rapidly in the ventral SCN than in the dorsal SCN. Scientists have now discovered that the neurotransmitter GABA excites the cells of the dorsal SCN but inhibits those of the ventral SCN. These opposing effects might influence the differing reaction times of these two sub-regions when someone travels across several time zones. This discovery thus opens new insights into the mechanisms behind the disturbing symptoms of jet lag. Ventral SCN influenced by external cues (Light) Dorsal SCN less affected by light

1 hour of time change = 1 day to adjust

Jet Lag If you travel by plane from (East to West) UK to USA leaving at 12:00 noon, you will arrive at 7:00 pm UK time when it is actually 2.00pm USA time. So, by 7:00 pm in the US, your biological clock is 12:00 midnight. All your biological rhythms are working on UK time. Your internal clock is telling you that it is midnight and you are ready to fall asleep. Melatonin is released, body temperature drops bodily arousal decreases Jet Lag is the time it takes to adjust and resynchronise The quickest way to adjust is to follow the local EZ’s (Phase Delay) delay sleep and stay up later. If you follow your EP (UK time) it will take longer to adjust – leading to more severe symptoms of Jet Lag. Phase delay = delay sleep Phase advance = sleep earlier

East to west, e.g. UK to USA West to east e.g. USA to UK Easier to Adjust More difficult to Adjust PHASE DELAY PHASE advance

East to west is always best! Phase delay – east to west e.g. UK to Mexico – we gain time. It is easier to lengthen our day (Siffre study, shift work research). Biologically ahead of local time – stay up later. Phase advance – flying east means the day is shortened, this is difficult to adjust to and symptoms of jet lag will be worse – go to bed earlier.

Circadian rhythms that adapt more slowly cope best with Shift Lag/Jet lag Other individual differences: …………………………. ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… ………………………………………………………………………

Unhappy and happy shift workers

Your conclusion is...

Treatment Research: Melatonin has been studied to treat jet lag and other desynchronisation problems (Takahashi et al., 2002)

What can we do? Blakemore 1988 found that a synthetic version of melatonin administered in the evening can reduced jet lag symptoms. Melatonin is available in USA and research is being carried out to see if it can be used to help aircrew. Read the case study p176. What are the problems of using melatonin to treat jet lag?

Write a summary of the Melatonin and Aircrew research studies. P.163/176 Eysenck No large enough clinical trials to evaluate long term effects Melatonin can help clock to adjust Use Melatonin only if you are in the time zone for 3 days Scientists claim that Melatonin use for Aircrew is inappropriate Re-synchronisation occurs only if ppt allowed to sleep after taking Melatonin Melatonin’s effect on motor and cognitive function is still unknown (the sedative effects are still unknown) Research is on going: US air force actively investigating its usefulness, aircrew participating in in exp. Study are not allowed to fly within 36 hours

Melatonin receptors are present on the neurons of the suprachiasmatic nuclei of most species. This suggests that the secretion of melatonin is regulated by a negative feedback loop. Experiments in which the administration of exogenous melatonin affected the circadian rhythm of locomotor activity in various rodents have also shown that this hormone can affect the functioning of the body’s biological clock.

Harma et al. (1994) and Suvanto et al. (1993) Harma et al. (1994) and Suvanto et al. (1993) examined the effects of a four day flight that crossed 10 time zones on the » Sleep » Alertness » Attentiveness » Body temperature » Salivary melatonin of the flight attendants Forty female attendants logged their subjective sleepiness and sleep quality each day. Their – Alertness – Visual task performance – Melatonin level – Body temperature was monitored every 2 hours They found that they became sleepier over the 4 days and had less sleep. Their cognitive ability varied too. Melatonin and body temperature delayed by almost 4 hours after the westward flight.

Fasting

BBC Jet Lag

Stop eating Fasting is the key

DMNH – Dorsal Medial Nucleus of the Hypothalamus The FEO (Food entrainment Oscillator) Scientists have long known that our circadian rhythm is regulated by our exposure to light. Now they have found a second "food clock" that takes over when we are hungry. This mechanism probably evolved to make sure starving mammals don't go to sleep when they should be foraging for food. The lead researcher Clifford Saper explains: The neat thing about this second clock is that it can override the main clock...and you should just flip into that new time zone in one day. It usually takes people a week to fully adjust to a new time zone or sleeping schedule. To think that this new "food clock" hack can help you change your internal clock in one day is mind boggling.

DMNH – Dorsal Medial Nucleus of the Hypothalamus The FEO (Food entrainment Oscillator) This will influence circadian rhythms when organism is starved for hours

How Do You Use This Trick? Simply stop eating during the hour period before you want to be awake. Once you start eating again, your internal clock will be reset as though it is the start of a new day. Your body will consider the time you break your fast as your new "morning." – For example, if you want to start waking up at 2:00 am, you should start fasting between 10:00 am or 2:00 pm the previous day, and don't break your fast until you wake up at 2:00 am. Make sure you eat a nice healthy meal to jumpstart your system. – Another example: If you are travelling from Los Angeles to Tokyo, figure out when breakfast is served in Tokyo, and don't eat for the hours before Tokyo's breakfast time. Combined with other hacks to help you get more sleep and be more productive, you can quickly adjust to any time zone.

Video clip: Fasting reset-your-sleep-cycle-overnight

Klein, Wegman and Hunt’s “Westbound” flights study (1972) Found that the adjustment of the sleep-waking cycle was faster when flying westbound. As the natural timeclock is 25 hours, it seems to be easier to have a longer day (phase delay) than 'back' in time (Phase disruption.)

Evaluation of research on disrupting biological rhythms Research findings Disrupting our biological rhythms has cognitive and emotional effects, as well as drastic consequences Methodological issues Studies have great ecological validity, however personality and individual differences are not controlled in those studies Real-life significance? Does it matter? Effects on cognitive abilities, such as attention and concentration negatively influence our intellectual and emotional well-being

Hw Describe the human endogenous pacemaker (biological clock) in control of the sleep wake cycle (6m). Describe one study of circadian rhythms (8m). What application to the real world has biological rhythm research got? (4m) Explain individual difference effects on Circadian Rhythm research (8m) Discuss research and explanations of the disruption of Circadian rhythms (16m) AO2/3 Evaluation/commentary