My top ten favourite things to do are as follows:
Now, I know why I like to eat – food tastes good. Also, if we’re going to be all ‘sciencey’ about it, humans have evolved to enjoy eating as we need the nutrition to survive. But why do we sleep? The answer is no one really knows. However, anyone who has ever pulled an ‘all nighter’, suffered insomnia or done a PhD can tell you sleep is certainly necessary. A lack of sleep leads to difficulty concentrating, an inability to focus and a lack of motivation which gets progressively worse the less sleep you get. And the only way to rectify this? To get some sleep.
It’s tempting to assume that we sleep to save energy, but this isn’t really the case. In fact we don’t save that much energy sleeping compared to just laying still. However, one thing we do know is that sleep is actually vital for the brain. That would explain the difficulty concentrating when you don’t get enough of it.
There are two main types of sleep: rapid eye movement (REM), which is when we have our most unusual disjointed dreams and non-rapid eye movement sleep (NREM) which usually brings fewer, more mundane, dreams. Unsurprisingly you can tell when someone is in REM sleep because their eyes dart around, whilst the eyes are relatively still in NREM sleep. Throughout the night we cycle in and out of these sleep stages (around 2-4 cycles every night), with the vast majority of sleep comprised of NREM. Scientists can monitor what stage of sleep people are in by looking at their brain wave (EEG) activity.
Yes, apparently brain waves are an actual thing. I’m not trying to be funny here – I genuinely had no idea these were real until earlier this week. I thought it was a saying like ‘being on the same wavelength’. Who knew? Everybody else in the world it would seem.
When brain cells want to communicate with each other they use electro-chemical signals which can be detected by neighbouring cells. Brain waves are simply the combined ‘firing’ of groups of brain cells. This collective ‘firing’ creates a voltage change large enough to be detected by electrodes placed on the scalp and this is the basis of the EEG. Peaks of synchronised firing are generally followed by periods of silence before moving to another peak, forming rippling electrical waves – brain waves.
During REM sleep brain waves are low amplitude, which means fewer cells are synchronised therefore producing a smaller signal. Waves which do occur in REM are also fast, meaning the cells are firing off electrical pulses more frequently. This pattern is very similar to the EEG signal seen when we’re awake.
Fun fact about REM: Species of animals with larger brains seem to require a higher percentage of REM sleep compared to NREM sleep. With tit-bits like that you’re sure to have as many friends as me! Two’s a lot right?
Anyway, REM is thought to be important for forming new spatial memories (like remembering how to get to that new bakery in town which sells those gorgeous pastries). Scientists also think that REM sleep may be required for the development of new brain cells in the memory forming region of the brain (the hippocampus). This is one of the processes which may be necessary for laying down new memories.
NREM sleep can be broken down into three stages. During the first stage, a state somewhere between sleep and wakefulness, brain wave activity starts to slow and switches to the high amplitude slow waves which characterise NREM sleep. During the second stage ‘spindles’ can appear. These are groups of large amplitude, irregular spikes in the EEG. It is thought that this high-amplitude activity represents periods when large areas of the brain are synchronised. This may be the perfect time for memories to be transferred between brain regions and may facilitate the incorporation of new memories into older existing ones. Interestingly schizophrenics show less spindle activity, but like many aspects of sleep, it isn’t really clear why. In the final stage, the brain has fully switched into slow wave. It is thought that during this stage new memories form. Slow wave activity is linked with the ability of brain cells to make new connections and ‘prune’ out old ones.
There is so much that absolutely no one understands when it comes to sleep. All in all I think this makes this topic incredibly interesting and, yeah I’m just going to say it – exciting. Ultimately though I’m quite happy that scientific research has unquestionably disproved the phrase ‘you snooze, you lose’.
Post by: Liz Granger
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Saletin, J.M.; Goldstein, A.N.; Walker, M.P (2011). The Role of Sleep in Directed Forgetting and Remembering of Human memories. Cerebral Cortex, 21, 2534–2541
Ferrarelli, F.; Huber, R.; Peterson, M.J.; Massimini, M.; Murphy, M.; Riedner, B.A.; Watson, A.; Bria, P.; Tononi, G. (2007). Reduced Sleep Spindle Activity in Schizophrenia Patients. The American Journal of Psychiatry, 164, A62