Sleep(less) in Leiden
More than 10,000 nerve cells in the brain see that we wake up in the morning and that we fall asleep in the evening. But what happens if this biological clock stops working properly? On 18 March the LIBC is organising a symposium on the latest scientific insights into sleep and sleeplessness.
Biological clock
‘It started as a fundamental research project, with a non-clinical question. Since then it has grown to become one of the most successful areas of medical research.' Neurophysician Professor Joke Meijer (LUMC) has made enormous advances in recent years in fathoming out the working of the biological clock. In the course of the study, it became steadily clearer how you can modify this clock. For example, as people age and their clock starts to show signs of wear. Meijer is one of the speakers at the ‘Sleep(less) in Leiden’ symposium, organised by the interdisciplinary Leiden Institute for Brain and Cognition (LIBC).
Pacemaker in the brain
Our natural sleeping and waking rhythm can be attributed to what Meijer calls a circadian pacemaker': a small organ in the brain that relaxes us at night and makes us active in the daytime. Individual nerve cells in this organ are genetically equipped to produce a sleeping and waking rhythm. In principle, it's a simple mechanism, Meijer explains. 'The genes in the cell nucleus produce proteins that are released in the cytoplasm of the cell. When the protein concentration reaches a particular level, the proteins form compounds and are channeled back into the cell nucleus. They then restrict the expression of the genes, causing protein production to decrease. But once the concentration drops to a particular minimum, the genes become active again. These swings take place over a period of some 24.5 hours.'
Neurophysiologist Professor Joke Meijer investigates the working of the biological clock in the human brain.
Light
24.5 hours? Doesn't that mean that our biological clock is always lagging behind our environment, then? Meijer: ‘If it's not corrected from outside, yes. Our clock has to be speeded up a little every day, which is something that light does. There is a connection from our eyes to our brain, directly to the biological clock. Light from outside can make some adjustments in the clock. When you open the curtains in the morning, for instance, and enough light falls on your retina, a chemical substance is produced in the biological clock. This speeds up the fluctuations brought about by the biological clock.'
Weekend
Without external adjustment, our biological clock would become further out of lsync with out environment. 'That's something you notice in the weekend, when you can go at your own pace and leave the curtains closed for longer,' says Meijer. Particularly around the age of 20 people tend to sleep in for longer. That, too, has a neurophysical explanation. 'The biological clock of adolecents naturally has a longer cycle time. That's why adolescents tend to go to bed later and get up later.'
Neural networks
Not only does the biological clock have to run synchronously with the environmental clock, the hands of the 10,000 individual clock cells also have to point in the same direction. Meijer: ‘Until ten years ago we thought that 24-hour rhythms were specifically determined by the molecular clock, the genetically determined ability of individual cells to produce rhythms. Electrophysiological research has demonstrated that this is an oversimplified version of the facts. It is crucial that the clock cells communicate adequately with one another. Individual cell mechanisms account for the production of very basic rhythms, but then the networks of nerve cells have to make sure that the clock works as an adaptive system. Neural networks have to see that the clock cells run synchronously with one another as well as in time with the rest of the outside world.'
Older people
It is precisely these neural networks that work less efficiently as people age. Older people sleep less well at night and find it hard to stay awake in the daytime. That has to do with how their biological clock works, Meijer discovered. 'We have indications that the rhythm-producing mechanism in nerve cells remains intact in older people, but that the communiction between the cells is no longer as effective. This is why the impetus to stay awake in the daytime weakens and the desire to sleep at night also lessens. The rhythm of the biological clock shows signs of levelling off.'
The rhythm of the biological clock levels off as we age This is why older people sleep less well at night and have difficulty staying awake in the daytime.
Physical activity
These are insights that are becoming increasingly applicable to the sleeping and waking rhythm of older people. 'Given the increased ageing of the population in the Netherlands, this is certainly an important issue,' according to Meijer. Her colleague, Professor Eus van Someren, a sleep researcher at the LUMC and the LIBC since November 2009. has shown that good lighting can improve the sleep quality of older people. Meijer is investigating whether physical activity can further improve their sleeping and waking rhythy. 'Our research points to the fact that physical activity, just like light, influences the working of the neural networks in the biological clock.'
Sleep and dreaming
Meijer will present her most recent findings during the symposium on 18 March. Eus van Someren, too, will make a contribution; he will talk about ageing, dementia and sleeplessness. Anyone wondering wny we actually need sleep, will be given the answer by German guest speaker Jan Born. He will show how sleep improves our memory by consolidating memories in the brain. And what about dreams? What is the purpose of dreaming? Tracey Kahan, from the Department of Psychology at Santa Barbara University, will explain what dreams tell us about the working of the mind. Leiden psychologist Professor Bernhard Hommel will conclude this second LIBC symposium, like that of last year, with some 'reflections of a sceptic.' Reason enough to remain awake and alert until the very end!
Thursday 18 March 2010, 9.30-17.00 hars
Leiden, LUMC, Building 3, Burumazaal
Participation costs € 30 (including lunch and coffee/tea)
Online registration form
Further information
Symposium programme
Leiden Institute for Brain and Cognition
(2 March 2010)