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Van Someren Group

Sleep, insomnia

About the Van Someren Group

Against the background of their 24-hour rhythm, driven by the circadian clock of the brain, sleep and wakefulness show a mutual dependency. The Sleep & Cognition group investigates how sleep affects brain function during subsequent wakefulness, and how experiences during wakefulness affect subsequent sleep. We aim firstly to elucidate factors that promote and disturb sleep at the systems level, notably insomnia, and secondly to investigate the brain mechanisms involved in the favorable and disruptive effects on cognition of, respectively, sleep and sleep disturbances. We think it’s important to translate fundamental insights into applications to improve sleep, vigilance and daytime function.

Human research tools include, in addition to the standard sleep-lab, brain imaging (high-density-EEG, MEG, fMRI on 1.5, 3 and soon 7 Tesla), transcranial magnetic stimulation (TMS), eye-tracking, computerized induction and assessment of task performance. The sleep-lab has a unique setup for comfortable skin temperature clamping in humans. An arsenal of ambulatory monitoring equipment is available. A web-based assessment tool for extensive insomnia and good sleep phenotyping has resulted in a growing database of, at present, 13000 people. The tool is available for other researchers that want to cooperate.

Eus van Someren:

‘A genetic disposition to be a night hawk or an early riser, a tendency to take, or not take, naps, snoring – none of it has much to do with the susceptibility to insomnia. The problem lies somewhere else. ‘A place for everything and everything in its place, is the expression, and this is literally the case when you sleep. In sound sleepers – people with a calm REM sleep – emotional events move from the emotional brain to the cognitive brain during that REM sleep. The experience is retained, but the accompanying tension is not. ‘In people with a restless REM sleep this reorganization does not work so well. Worse than that: if they have a disturbed REM sleep all through the night they may wake up feeling even more anxious than when they went to bed.

‘That it works this way can be seen when people are asked to reminisce on embarrassing events that took place a long time ago. When asked to recall a humiliating experience of thirty years ago, the emotional brain of poor sleepers lights up as if it was happening right now. Conversely, sound sleepers showed a great deal of activity at the front of the brain, where the “cognitive controller” resides. They also remember the experience, but it does not activate their emotional brain.‘We see restless REM sleep not only in insomniacs, but also in people susceptible to PTSS (posttraumatic stress syndrome) and in people suffering from depression or anxiety disorders. The process of clearing away emotional tension is a problem for all these people. But which underlying brain processes might be causing this?

‘It may be like this: In the brain stem lies the locus coeruleus (LC), a brain nucleus that is involved in alertness, attention and emotion. The LC continuously produces noradrenalin – a substance that ensures you are alert, but not during REM sleep. On the basis of animal research, we now think that the LC in people with restless REM sleep does in fact continue to produce noradrenalin. ‘While you sleep, connections in your brain are reinforced or cleared away. Noradrenalin supports the reinforcing. Weakening is really only possible if the LC stops producing noradrenalin, i.e. during REM sleep. If your LC keeps humming away while you sleep, it may be that connections are reinforced that really ought to be weakened. ‘That would agree with what we see: that people with a restless REM sleep sometimes wake up feeling worse than they did when they went to bed. It may be that something that should have been eradicated during their sleep is in fact consolidated. For people with anxiety this would be feelings of anxiety, and for people with depression it would be a feeling of wretchedness.

‘It is my dream to test this hypothesis. If it is correct, it would mean that insomnia is not a sleeping disorder but an emotional memory disorder – just like anxiety and depression. We already know that the risk genes for insomnia, anxiety and depression lie very close together. I am therefore very hopeful that I will finally learn what it is exactly that makes insomniacs suffer.’

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