Why we Dream and the Role of Sleep, Circadian Rhythms and The Body Clock

17 October 2004
Presented by Adel Fattah, Chris Smith


In this show dream expert and psychologist Dr. Mark Blagrove, from the University of Swansea, joins us to discuss why we dream, and how what you read about or do during the day can affect your dreams. Also joining us is body-clock scientist Dr. Mick Hastings, from the Cambridge MRC Laboratory of Molecular Biology, to talk about why we sleep, have a body clock and a sleep-wake cycle (also known as the circadian rhythm).

In this episode

A test tube containing a blood sample

- Device Helps Phlebotomists Find Veins

Doctors, phlebotomists, and vampires could soon have a new tool at their disposal to help them find suitable veins for taking blood or inserting a drip...

Device Helps Phlebotomists Find Veins

Doctors, phlebotomists, and vampires could soon have a new tool at their disposal to help them find suitable veins for taking blood or inserting a drip.

Biomedical scientist Herbert Zeman, from the University of Tennessee in Memphis, this week unveiled a new device which uses near-infrared light to scan the skin for juicy veins.

An image of what the camera sees is then projected back onto the patient's skin, producing a blood vessel 'road-map' to guide doctors to the best sites for inserting a drip, or collecting a blood sample.

The machine illuminates the skin with an array of near-infrared LEDs, which are clustered around the camera and emit light at a wavelength of 740 nm.

Light of this wavelength is strongly absorbed by blood, but scattered and reflected by other tissues. So blood vessels look dark whilst the surrounding tissues look much brighter.

Set up correctly, the new device, which is about the size of a shoebox, can 'see' up to 8mm into the skin, and pinpoint the position of a vein with an accuracy of 0.06mm (1/20th of a mm). It is likely to prove particularly useful for young children because their veins are often difficult to locate due to their small size and the presence 'puppy fat'.

Lightning Helps To Genetically Modify Bacteria

Scientists often give bacteria an electric shock in the lab in order to encourage them to take up extra pieces of DNA, called plasmids, which are used in genetic engineering experiments. But now, according to French researchers, lightning achieves the same feat. Timothy Vogel and Pascal Simonet, from Lyon, subjected common ground-dwelling bacteria to artificial lightning strikes. Any bacteria close to the site of the strike are obviously fried, but those further away receive a milder shock that encourages them to pick up pieces of DNA 'bait'. So far the experiments have worked with laboratory strains of E. coli, and another common bug called Pseudomonas. The researchers think that the process is widespread and helps bacteria to evolve by enabling them to scavenge pieces of DNA, containing foreign genes, from their surroundings. It may also have helped to kick-start the evolution of some of the first bacteria. Click here to jump to the text Article by Jemima Stockton about probiotics and 'friendly bacteria'

Seeing light beams and working with lasers are among the things that attracted Prof. Giessen to the field.

Light-fingerprint Helps To Pick Up Explosives From a Distance

Would-be terrorists could have their evil work made harder in the future, thanks to new advances in explosive detection by Florida scientists...

Security forces need to find explosives quickly, inexpensively and reliably: there is no room for error when you are dealing with determined terrorists. Also, false positives - thinking that there is a bomb when there isn't one - could cause panic and delays.

Current explosive detection methods require a swab or sample to be taken from a person or object that might have been in contact with explosives, which is then analysed in the lab.

Now, researchers have been applying a technique called photoluminescence spectroscopy, where light is shone on a substance, and a detector measures the characteristics of the light that gets sent back.

The chemical structure of the material affects what happens to the light, so every chemical has a special spectroscopic signature.

The Florida team found that TNT and other common explosives shared a highly specific signature. This means that in theory, light shone at a distance on objects such as boats, people or suitcases could reveal whether they had been in contact with explosives, marking them out as a suspect and allowing security forces to swoop.

Rolf Hummel, the brains behind the project, says that once it is fully developed, the new method would be cheap, accurate and quick.

The Body Clock And The Sleep / Wake Cycle (circadian Rhythm)

The body clock comprises a tiny cluster of nerve cells sitting in the hypothalamus, which forms the base of the brain. This group of a few thousand nerve cells switch on and off groups of genes in a feedback loop lasting 24 hours. The expression of these genes alters the activity of the nerve cells which therefore effectively 'keep time'. The time registered by the body clock is then used to control the release of other hormones which are concerned with preparing us for activity or rest respectively, and in controlling the parts of the brain involved with alertness and arousal.

Luckily we don't suffer permanent jetlag when we go abroad because the clock can be reset by exposing our eyes to light. A small number of nerve fibres from a specialised group of light-responsive cells in the retina feed in to the body clock and can adjust the rhythm, according to whether it is light or dark, just as one would alter a wristwatch. This system allows the clock to adapt to changes in day length and the demands of modern-day living, but the system is not perfect and does not kick in immediately, which is why we feel jet-lagged after a long haul flight, or after working a night-shift.

Why Do We Dream, And What Affects What We Dream About ?
with Dr Mark Blagrove

Chris - why do we think dreaming is so important and why do we have problems remembering our dreams?

Mark - We are not sure yet why we dream or what it does. You're more likely to dream during rapid eye movement sleep or REM sleep, which is when your brain waves look like you're awake but your body is flat out. We know that when you wake people up from REM sleep, people are able to solve anagrams and puzzles quickly. REM sleep is also associated with memory, so it could be that you're laying down memories in REM sleep as well, which is what our brain is doing. What your dreams are doing during REM sleep, we don't know, it could be they're telling us what our brain is doing during REM sleep or it could be a lot of chaos. It's not quite that chaotic - samples of people's dreams have shown they are related to their lives and the dreams are sensible and have a purpose. In the case of remembering them though, there are parts of the frontal lobe which switch off during REM sleep, and these bits are related to laying down memory and critical thinking, so it may be that we're just not paying attention while we're dreaming. The other possibility is that our brain chemistry just won't allow us to remember our dreams or possibly we have evolved to not be able to remember our dreams, because we may spend too much time in the day thinking about the meaning of our dreams!

Chris - and what about nightmares ?

Mark - There is a worldwide search going on at the moment to find out why some people have more nightmares than others. If people are stressed or live through stressfull experiences like earthquakes and things like that they do have more nightmares than others. On the whole if you look at how stressed, anxious or depressed people are the relationship between that and the number of nightmares they have is really quite small. So it looks like we are almost designed to have some bad dreams even if our lives are actually quite okay.

- Why it is that you sometimes see two rainbows in the sky?

why it is that you sometimes see two rainbows in the sky?

Why it is that you sometimes see two rainbows in the sky?

When light from the sun shines into a raincloud, it hits a raindrop, goes inside the raindrop, reflects off the opposite inside surface of the raindrop, and then leaves from the front again. Just as in a prism, as the light leaves the raindrop it is split up into its constituent colours of the spectrum, producing the first rainbow you see. But sometimes when the light is very bright and the sky very dark you can see a second rainbow outside the first one and if you look very closely you'll see this is in fact a mirror image of the first rainbow. The reason for this is that after it has bounced off the back of a raindrop, some light is reflected back off the front of the raindrop again and repeats the whole process, completing the journey twice. As a result, when it finally leaves the front of the raindrop it emerges at a different angle and as a mirror image, producing a second rainbow outside the first.

- Does the sun affect the tides like the moon?

Does the sun affect the tides like the moon?

Does the sun affect the tides like the moon?

Yes, but to a lesser extent than the moon, which is the main determinant of our tides. You can work out if we are on a neap tide or a spring tide - that's a high tide or a low tide - depending on whether these two celestial bodies line up with each other. When the sun is in alighnment with the moon we have a new moon (which means you can't see it because it is not illuminated and is dark) and the two bodies work together gravitationally, producing a spring tide. Two weeks later, however, the moon is at 90 degrees to the sun, so they're not in alignment, so you have a neap tide. Two weeks after that you have a full moon and the two are working together again, and you have a spring tide.

What causes sleep apnoea?

You are lucky to have had it diagnosed because lots of people with it and are undiagnosed. People who have apnoea stop breathing, maybe hundreds of times a night, which means that your brain is regularly starved of oxygen producing symptoms of tiredness, poor concetration and irritability the next day. There is a way of treating this and that is to wear a mask which pushes air down into the lungs under pressure - maybe your doctors have told you about this - but you'd need to use this every night for life. There are two possibilities for what causes sleep apnoea: central apnoea is where the bit of the brain which tells you to breathe whilst you're asleep switches off - but this is rare. More common are problems in the throat so when you fall asleep your muscle tone goes away and your throat collapses, obstructing the airway. This is why pushing air down with a mask can help. People who have this can have surgery to correct it, but the surgery is fairly major.

- Why does sleep deprivation cause red eyes?

I'm getting less and less sleep due to back pain and recently I developed red and dry eyes - what can you recommend?

Why does sleep deprivation cause red eyes?

This could be that you have a small viral infection of the eyes and a bad back, or there is a disorder called Ankylosing spondylitis, which is caused by the immune system attacking the body itself. This is a progressive back condition which can have dry eyes associated with it, although not usually a sudden onset as in your case. There is a blood test that can help to confirm this, so it is best to go and see your GP and discuss this possibility.

Why don't I ever dream?

Surveys have shown that about 6% of the population say that they absolutely never dream. There doesn't seem to that much difference between them and the rest of the population, but what has also been done is take some of these people and wake them up in sleep lab when they're in REM sleep. Every 90 minutes or so during your sleep the majority of people go into REM sleep, so you put these people in the lab, wire them up, and what happens is that you can wake people up during these periods of sleep when they ought to be dreaming. With most people you've got about an 80% chance of a dream being reported if you wake them up like this. Now if you're a non-reporter of dreams, that is one of the 6%, what's been found is that 0.6% of these absolutely never report a dream even if you wake them up during REM sleep, so in your case Betty, it is quite possible that you are having dreams and you just don't remember them.

- Do the Swiss get the day off if their biorhythms go off kilter?

is it true that people in Switzerland get the day off if their biorhythms go off kilter?

Do the Swiss get the day off if their biorhythms go off kilter?

We don't know about this, but they should! Tube drivers for instance don't get much daylight so this is bound to have an impact on your biorhythms. Night shift workers tend to be more accident prone, and the sleepier you are the more likely you are to be overconfident. There have been studies that show that for nurses in the US, there was a 20% greater incidence of breast cancer which may be due to the cortisol they're producing.

What causes narcolepsy?

Narcolepsy is the disorder where people fall asleep repeatedly during the day and there seems to be genetic component to this. Luckily there are drugs which can be used to treat it. There can be frightening aspects to narcolepsy, for instance people have been known to suddenly fall down as they fall asleep, or have nasty hallucinations as they fall asleep. The brain chemistry behind it is better understood now, and we do know about the genes that are linked to this. One particular chemical is a substance called hypocretin, and people with narcolepsy tend to have problems with the receptors for this brain chemical, or an abnormal form of this chemical. There are also people with 'clock' genes that give them a faster or slower body clock, but this shouldn't be mistaken for narcolepsy.

- Can viral infections affect sleep?

I've been diagnosed with a phase delay sleep disorder following Glandular Fever, and I've tried various ways to keep my sleep normal with...

Can viral infections affect sleep?

Viral infection can affect your brain, and body clock, which may be the cause here. The body clock is in the part of the brain called the hypothalamus, so infection and high body temperature around this area could affect your body clock. In your case though, it seems that your body clock does work, it's just maintaining it that is the problem.

Why don't I get tired ?

Lucky man ! This is to do with the amount of sleep that people get in the first place. Deep sleep and REM sleep is the key. The more people get of this the less sleep they need, which is why people sometimes say they only need 4 or 5 hours sleep rather than the standard 8 hours.


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