Sleep appears to help the laying down of memory through new brain cell connections

I regular reader of this website (Chris) alerted me today to this BBC website report of a study which focused on the impact of sleep on memory. The study itself was conducted in mice [1]. The animals were taught a new skill (walking along a rotating rod). Then their brains were examined overnight. During sleep, cells in the cortex of the brain (the outermost later of the brain which governs, among other things, movement) sprouted new connections. These new connections are thought to be the physical manifestation of memory. During sleep, these pathways actually fired again too, as if the brain was replaying the newly learned skill in order to consolidate it.

However, in a sleep-deprived state, these connections did not form in the same way.

The formation of new neurone-to-neurone connects during sleep has not be demonstrated before, and the researchers involved in this study believe that this observation helps explain previous evidence suggesting that sleep has an important role in the formation and retention of memory.

The researchers involved in this study went further, by attempting to ascertain what type of sleep appeared to be important for the formation of new brain cell connections. There are essentially two types of sleep:

1. REM (rapid eye movement sleep)

REM sleep is relatively shallow sleep, during which we are usually dreaming and the brain is surprisingly active. In REM sleep, brainwaves have a frequency of about 8–12 cycles per second (hertz) – about the same as when someone is awake but in a relaxed state.

2. Non-REM or ‘slow-wave’ sleep

During non-REM sleep, sleep is deeper and the brainwave frequencies are slower (often 4–7 hertz, but sometimes even slower than this). The brain is relatively quiet during non-REM sleep, but there can still be a lot going on in other departments. For example, it’s during non-REM sleep that the body secretes ‘growth hormone’ from the pituitary gland at the base of the brain.

Traditionally, adequate REM-sleep has been identified as important for memory. However, in this recent study, it was actually deeper non-REM sleep that seemed to be important for the formation of new connectivity in the brain.

However, it’s also perhaps worth bearing in mind that this study was performed in mice, and that none of its findings therefore have automatic relevance to memory function in humans.

What this study does do, I think, is underscore the fact that while sleep looks like quiet time during which not much is happening, it is in fact an active time during which processes are taking place that promote good physical and mental functioning. Part of sleep’s function is to prepare us physiologically and psychologically for the next day. Looked at like this, sleep appears less of a ‘waste of time’ and more of an essential ingredient in health and wellbeing.


1. Guang Y, et al. Sleep promotes branch-specific formation of dendritic spines after learning. Science 2014;344(6188): 1173-1178

10 Responses to Sleep appears to help the laying down of memory through new brain cell connections

  1. Mike Sheldrick 6 June 2014 at 2:53 pm #

    Somewhat off topic, but I continue to wonder about the proper amount of time we need in sleep to optimize health. I can agree that we need some amount of sound, undisturbed sleep, but is there any basis at all for the insistence that we need eight hours of it. What proportion of REM and deep non-REM might this be? Is it possible that the person getting say, four hours of deep non-REM sleep is better off than someone who gets only two? What about other sleep modes, like a two-hour afternoon nap, coupled with six hours at night.

    Seems to me that sleep studies are still in their infancy, even though we’ve been working seriously on them for — oh I don’t know, 50 years.

    Personally, I find it difficult to sleep more than 6 hours, don’t feel tired for most of the day, but when I do, I can usually take a nap. Have no idea how healthy this is or how to train myself into a healthier pattern.

    • Robert Park 6 June 2014 at 3:44 pm #

      Like yourself Mike, I too do not require eight hours undisturbed sleep yet my wife does. I am certain that the different requirements are connected to early learning habits and beliefs. Obviously there will be a common denominator in sleep patterns but is there a placebo effect occurring too?

      This YouTube video may interest you:

  2. Robert Park 6 June 2014 at 3:32 pm #

    This research serves to substantiate common knowledge; cerebrally there is probably little difference between the adaptations of mice and men. An interesting feature of the brain is that if it has nothing to occupy it, it creates fiction. The first thing the brain does when the body goes to sleep is to recreate recent events, especially those which confuse or are emotionally upsetting; in each situation it repeatedly re-enacts the scenario in an attempt to resolve the issue confronting it. Sometimes those dreamscapes are in allegorical language the signs which, although universal, are unique to the dreamer depending on culture and experience within society. There appears to be a connection between the emotions, which has its own intelligence, and that of the intellect, which when sleeping interact with each other; the instinct and the logic. As an amateur enthusiast in dream analysis I learned this from experience and observation rather than from academic study.

  3. jean humphreys 6 June 2014 at 8:38 pm #

    I normally take a nap after lunch. What happens is that I nod off in my armchair, with the cryptic crossword in one hand, and my pencil in the other. If it has been a tricky crossword, with quite a few clues that I just don’t “get”, I find that they will have solved themselves in the back room of my brain, and, as soon as I wake, I am filling them in without even thinking.

    • CJP 7 June 2014 at 9:10 am #

      That’s a good point well made Jean.

      In people that have tasked their brain with solving a problem the solution may drop out of whatever it is that goes on while they ‘sleep on it’, and creative thoughts or links may come to mind upon waking. Some people keep a notepad and pencil by the bedside in case memory throws up a ‘todo’ that had escaped memory but re-entered the consciousness in the course of sleep.

      An acquaintance of mine once equated the brain to a muscle. ‘The more you work it the stronger it gets.’ But as many an athlete knows the harder you train the more sleep and recovery the body needs – marathon runner Paula Radcliffe is reputed to have slept for 12 hours while in training.

      What I take from this is that intelligence, and the learning of higher order abilities, may work a bit like physical training. The ‘recovery period’ in between training sessions matters as much as much as does the quality of work undertaken while training – and this could be as true for mental development as for physical development.

      Athletes that underestimate the need for rest and recovery between training sessions find that in time they may be beleaguered by injury. High achievers in the workplace that ‘ thrive of stress’ and that do not allow enough respite may find that stress catches up with them over the run of time, suffering adrenal fatigue, depression, or heart attack down the road. [Sir Stephen Redgrave ranks in my mind as a possible instance of over-training.]

  4. Vanessa 6 June 2014 at 8:53 pm #

    I’m not surprised that this phenomenon takes place during non-REM sleep, after all if the brain is active and ‘firing’ while we dream, it’s not likely to be laying down new pathways with all that going on……a bit like trying to get your computer to do something useful while it’s busy doing something else…..then needs defragging because all the stuff ends up all over the hard disc in random bits!!

    I do know that I find I can recall new things better after a good night’s sleep – so maybe it doesn’t just happen in mice.

  5. Rosie 13 June 2014 at 10:38 am #

    I’ve just come across this thread, so sorry for the delay in putting my two cents in.
    This subject has always interested me and I have a question that I haven’t been able to find an answer to yet.
    I sleep around 7 hours a night but almost always wake up tired because I seem to have been dreaming all night. I reckon I view the equivalent of at least 2-3 full length movies each night! Does this mean I’m missing out on the important non-REM sleep? Does this help to explain why my memory has never really been perfect and why I’m not that tall (160 cm)? My husband is usually amazed when I subject the poor man to a blow-by-blow account of my dreams.

    • Christopher Palmer 14 June 2014 at 11:39 pm #

      is the bedroom quite dark?
      even faint light may alter some hormonal balances.
      plus a hormone called cortisol should follow a cycle each day.
      I would recommend ‘earthing’, visit to get a sense what that means. There is a book too, well worth the read. The reviews on Amazon may encourage.
      If you or your man feel competent you could rig a conductive ankle band and have that wired to ground. If you ain’t sure don’t try. Earthing sheets are available, but an inexpensive antistatic band is as good and can be linked to proprietary bonding plug. Earthing can potentate certain meds so heed any advice from their website.
      earthing has been demonstrated to normalize cortisol, and the cascades that follow May hare you feel brighter.
      CoQ10, garlic oil, and turmeric caps help me feel sharper and energised.
      let on how you get on.

      • Rosie 21 June 2014 at 9:06 am #

        Christopher – Actually, my bedroom is very dark as I live in the countryside, so no or very low ambient light. I’ve not heard of earthing but will take a look as you suggest. My question was more to do with the effects of missing out on non-REM sleep as opposed to REM sleep, as I seem to spend all night dreaming and my memory has never been terrific, though it has got me through school, college and work very nicely;) So I wondered if the two might be connected.

  6. Robert Park 13 June 2014 at 2:17 pm #

    Dreaming should not cause you to awake tired but harbouring worries which would manifest themselves in dream would more likely be the cause and particularly so if your normal thoughts tend to be negative when those fears would manifest themselves in the dreamscape. This is often a feature of those who have experienced trauma in their early lives or who feel they have lost control of their present lives. Do not take this comment too literally as even a nutrient deficiency or aging or a health problem could cause you to feel tired upon awakening. If you look for lucid dreaming on the Internet search engine you might find something of interest that may help. Finally, what is a perfect memory and 5 feet 3 inches in height, by itself, sounds perfect!

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