Earlier this year, The Goodnight Co. team attended The University of Queensland's sold-out event, The Science of Sleep. We caught up with one of the speakers, Associate Professor Bruno van Swinderen from the University of Queensland's Queensland Brain Institute, to explore the mystery of why we spend approximately one-third of our lives (roughly twenty-five years) asleep, in our most vulnerable state.
1. Why do we need to sleep and what do different stages of sleep achieve?
All animals need sleep, not just humans. There are several hypotheses being tested as to why sleep is crucial, and why there are different forms or stages of sleep even in tiny insects. We suspect that for brains to work as efficiently as they do when we are awake, there is a cost, or a price to pay. One idea that has been proposed is that ‘sleep is the price we pay for plasticity’.
What this means is that to be able to learn, our brains need to physically change, and sleep ensures that these changes at brain synapses (points of chemical communication between brain cells, or neurons) are optimised and maintained within a narrow range. Our brains need time to do this, to physically change, in the absence of outside stimulation — which could explain one function of deep or ‘slow-wave’ sleep.
But sleep has multiple functions, for example, REM sleep (when we dream) could be more related to the optimisation of circuits in the brain, as opposed to the optimisation of individual cells. Within the brain there exist subsets of neurons that form groups or systems that control different functions. REM sleep could be much more related to these systems, for example, optimising emotional learning and maintaining our capacity for subjective awareness. In this way, REM sleep might be the ‘price we pay for being conscious’ — this idea raises interesting questions about consciousness in animals that have such a sleep stage.
2. What is the difference between natural sleep and the sleep that is a result of medication?
Natural sleep is an ongoing alternation between different sleep stages, including deep and REM sleep. This cycling changes over the course of the night. It’s a really complex biological phenomenon with a natural dynamic and architecture. In contrast, typical sleep drugs are more like an on/off switch and put the brain into deep sleep without REM sleep, and result in unconsciousness without any of the inherent complexities of natural sleep. None of the current sleep drugs even come close to replicating the complexity of natural sleep and cycling between different sleep stages.
3. Why study fruit flies and their sleep?
The discovery that Drosophila, or fruit fly, sleep means that we can now treat sleep as an experimental variable. Fruit flies have a simpler brain, and have one of the smallest brains that still needs sleep and that sleeps in different stages. There are many genetic tools that have been developed for the fruit fly brain, which simply aren’t available to the same degree in mammals. In the fruit fly, we can target the neural mechanisms that are relevant for sleep by turning them on and off when we want. In this way, we can determine exactly what sleep does for a brain, and for animal behaviour in general.
4. How does our environment affect our sleep?
Many environmental factors influence our sleep. Artificial light is completely unrelated to how we have evolved. There are light receptors in our brain that need to be exposed to darkness and therefore downregulated well before you attempt to sleep. Stress and nutritional status also have a huge impact on our sleeping patterns.
But it isn’t only about negative environmental factors. To go back to the hypotheses of why we even sleep at all, what we experience during the day obviously affects our sleep. This is at the heart of the hypothesis that sleep is the price we pay for plasticity. If we need sleep to process our waking experiences and to determine which changes should be kept and integrated permanently into the brain then, by definition, our experiences during our waking hours must influence our sleep duration and quality.
5. How could we harness the restorative power of sleep as a potential therapy option for illness and injury?
This is a difficult question in humans because of how our sleep drugs work by mostly only inducing deep sleep. It is unclear as to whether we can harness the restorative power of sleep if we can’t replicate the complexities of natural sleep cycles. To realise the potential of sleep as a restorative treatment, we need to understand how to mimic natural sleep artificially. Or we need to understand the various sleep functions and tailor those to different brain needs as required.
Our discovery that fruit flies have different sleep stages means that we can potentially study those different sleep functions separately. By understanding these different functions, we could then develop drugs that come closer to approximating natural sleep cycles. We have already found that learning and attention can be restored in defective flies by making them sleep more via an insomnia drug that was intended for humans. This groundwork will hopefully pave the way to improving our understanding of sleep processes in humans and how we can harness the restorative power of sleep in injury and disease.
Associate Professor Bruno van Swinderen
Bruno received a PhD in evolutionary biology from Washington University in St Louis, Missouri. His postdoctoral work at the Neurosciences Institute in San Diego, California led him to the scientific study of consciousness. Taking an evolutionary view, he developed novel paradigms to study perception in the smallest animal brains. His discoveries include uncovering neural correlates of sleep and selective attention in flies, as well as fundamental mechanisms of general anaesthesia.
In 2008, he moved to Australia to run a research lab in the Queensland Brain Institute at the University of Queensland. His lab uses flies and bees to understand how the brain is able to block or prioritise sensory stimuli, as happens during sleep and attention. He is particularly interested in how sleep and attention might have co-evolved to optimise behaviour, and is keen to promote research in simpler animal models to understand complex brain processes.
This article was reshared with permission from Queensland Brain Institute Read the original article here.
You can also read more about the science of sleep here.