Sleep, memory and schizophrenia
We've heard how sleep plays a pivotal role in making our memories strong and resilient but, well it is a little complicated! And if something's that complicated then there are many ways for it to go wrong. Many people don't realise but one of the most debilitating symptoms of schizophrenia is actually the mental impairments particularly memory loss, so has this got something to do with sleep? Connie Orbach met Dr Ullrich Bartsch at Bristol Univeristy's sleep lab to find out...
Ullrich - We've got an MRI scanner over there and the facility for experimental rooms and meeting rooms.
Connie - A sleep lab is exactly what you might imagine. It's a bit like a hospital - there's a bed, a bathroom and well... then there's all types of kit to monitor you muscle tone, your brainwaves, eye movement and infrared cameras to watch you while you sleep. So maybe a bit more creepy than a hospital. And next door to this room is where Ullrich Bartsch and his colleagues will sit for hours on end, night after night, measuring their patients quality of sleep by the different patterns of brainwaves detected.
When we sleep, we cycle through different stages. First very deep, slow wave sleep... Next we move into lighter sleep, characterised by bursts of spikes called sleep spindles and finally... REM sleep - smaller faster waves. Okay, but I know what you're thinking... What on earth's all this got to do with memory and schizophrenia?
Ullrich - Sleep has been shown in the past 10 or 20 years to be important for memory consolidation and one of the biggest problems in mental health, particularly in schizophrenia, is the treatment of cognitive deficits. And one intriguing fact that has long been anecdotally reported is that schizophrenia patients will initially start losing their regular sleep pattern before their psychosis kicks in. That is mainly the loss of one particular oscillation that occurs during sleep and these are these spindle oscillations that I've mentioned earlier.
Connie - Schizophrenics show less of one particular type of sleep wave - the spindle. And as Matt said, patterns of brain wave are important for memory but how do we show that's really what's behind their forgetfulness. Well, that brings us back to the sleep lab... Ullrich takes healthy people and pre-symptom schizophrenics and gives them a simple movement task. Thinking I had an opportunity for a fun test, I decided to give it a go myself. I had to type out a five digit sequence as fast as possible over and over again... 14132, 14132, 14132, 14132, 14132... You get it. I did this twelve times with a break between each trial. Over the twelve tests people improved but the real kicker is that after a nights rest when they do the task again, they have improved a lot more.
Ulrich - In the motor task, I think you can reach up to 30-40% improvement.
Connie - But what about schizophrenics? Well interesting, when they sleep, they don't improve at all.
Ulrich - So the spindles, that I've mentioned earlier are, in fact, correlated with the amount of improvement that you show the next morning after you've slept over learning a motor task.
Connie - So the more spindles you have the better your improvement - is that right?
Ullrich - Yes, that's correct.
Connie - If I remember correctly, you were saying that in schizophrenia that schizophrenics have less of these spindles during sleep and so what does that mean when you get schizophrenics to do this task?
Ullrich - So they, first of all, perform much worse on the motor sequencing task. So their initial learning is already lower, so they would have difficulties with motor coordination but also, if they would sleep for a night and wake up the next morning and be tested again, they would not have improved in that particular task.
Connie - Not have improved at all?
Ullrich - They wouldn't have improved at all. Of course, there are some participants who do better than others but on average, if you take a relatively large group of schizophrenic patients, they would show little or no improvement. The idea is that because they have less spindles, they cannot process the information that they've taken up during a day as well as during sleep and they can, therefore, not strengthen these memories during sleep and then cannot show improvement in the task the next morning.
Connie - Now we know that what can we do? Can we just get them to sleep more? Instead of eight hours of sleep at night, why don't we get them to do ten hours sleep a night?
Ullrich - Unfortunately, it's not that easy because you need the right type of sleep. So, as we said, there are different stages and stages and sleep spindles are particularly characteristic of that particular sleep stage. In the case of schizophrenics, there are other things that we could do, so we could make the sleep more continuous. Most schizophrenics will have fragmented sleep but also we could try and bring back some of the missing oscillation, if you will, so there might be a way of using pharmacology. The right pharmacology (the right sleeping pills) to bring back the right oscillations during sleep. Another promising concept for enhancing oscillations during sleep is actually electrical stimulation or magnetic stimulation. A recent technology has emerged where people can use magnetic pulses, which is called transcranial magnetic stimulation, to actually induce activity patterns of brainwaves in brains of healthy people but also it's beginning to be used in clinical populations.
Connie - Clearly sleep and memory are intrinsically combined, impossible to separate but what about the rest of us. I asked our sleep expert for a few tips.
Ullrich - If you have to take in a lot of information and you have to remember it the next day, it's probably good to have either have individual naps in between in the afternoon, so that will definitely help your brain to pack the influx of information nicely.
Connie - Individual naps between study; Who knew that students had it right all along!
Ullrich - Yes, they were doing the right thing and especially the young brains need even more sleep than the older brains.
Connie - I'll tell my boss and start petitioning to get beds put in at work.
Ullrich - Yes, well if only. I would be happy to sign a letter if you need some support.