Category: Memory

Tetris could prevent post-traumatic stress disorder flashbacks (but quiz games make them worse)

By Ed Yong | November 10, 2010 5:00 pm

TetrisThis is an updated version of one of my favourite stories from last year, edited to include a sequel study that develops and expands on the first one.

You’ve just been in a horrific car crash. You’re unharmed but the vividness of the experience – the sight of a looming car, the crunching of metal, the overwhelming panic – has left you a bit traumatised. You want something to help take the edge off and fortunately a doctor is on hand to prescribe you with… Tetris.

Yes, that Tetris. According to Emily Holmes from the University of Oxford, the classic video game of falling coloured blocks could prevent people who have suffered through a traumatic experience from developing full-blown post-traumatic stress disorder (PTSD). As ideas go, it’s practically the definition of quirky, but there is scientific method behind the madness.

Every traumatic experience flips a mental hourglass that runs out in about six hours. After that time, memories of the original event become firmly etched in the brain, greatly increasing the odds that the person will experience the vivid, distressing flashbacks that are the hallmark of PTSD. But the brain, powerful though it is, only has so much processing power available for laying down such memories. If something can be done soon enough to interfere with this process, the symptoms of PTSD could potentially be prevented.

Tetris, it seems, makes an ideal choice for that. To position its rotating blocks, players need good “visuospatial skills” – they need to see, focus on, and act upon the positions of different objects, all at high speed. These are the same sort of mental abilities that provide the foundations for flashback images.

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Study raises questions about the role of brain scans in courtrooms

By Ed Yong | May 10, 2010 3:00 pm

Brain_scanA murder suspect sits in a quiet room with electrodes placed on her head. The prosecution reads out its narrative of the crime and the suspect’s alleged role in it. As she listens, the machines record her brain activity and reveal that she experienced aspects of the crime that only the murderer could have. Her own memories, teased out by technology, have betrayed her. The verdict is guilty.

This scenario might seem far-fetched, but it actually happened in an Indian trial that took place in 2008. The judge took a brain scan as proof that the suspect had “experiential knowledge” about the crime that only the killer could have possessed. She was sentenced to life in prison. There has been a smattering of attempts to use brain-scanning technology in this way, accompanied by an uproar about the technology’s readiness.

Now, a new study by Jesse Rissman from Stanford University confirms that promises about the social implications of brain scans are overplayed. Together with Henry Greely and Anthony Wagner, Rissman has shown that brain scans can accurately decode whether people think they remember something, but not whether they actually remember something. And that gap between subjective and objective memory is a vast chasm as far as the legal system is concerned.

Our memories are stored within networks of neurons so it’s reasonable to think that by studying the patterns of activity within these networks, we should be able to decipher individual memories. Studies have already started to show that this is possible with our existing brain-scanning techniques, and with every positive result, the temptation to use such advances in a practical setting grows.

The courtroom is an obvious candidate, especially because our brains respond differently when it experiences something new compared to something old. You could use brain scans to tell if someone has actually seen a place, person or thing, reliably corroborating the accounts of witnesses and suspects without having to rely on the vagaries of accurate recall and moral fortitude. For this reason, techniques like functional magnetic resonance imaging (fMRI) have been enticingly billed as the ultimate in lie detection technology. Claims of “mind-reading machines” and “psychic computers” have abounded in the press.

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To sleep, perchance to dream, perchance to remember

By Ed Yong | April 22, 2010 12:00 pm

MazeIt seems obvious that thinking about something will help you to remember it better, but it might be more surprising to know that this process works even more efficiently when we’re asleep. Erin Wamsley from Harvard Medical School has shown that people who are trained to navigate a virtual maze learn the best route through it more quickly if they dream about their experiences.

The last decade of research has clearly shown that sleep is one of the best aide memoires that we have. During this nightly time-out, our brain can rehearse information that it has picked up during the day and consolidate them into lasting memories. Wamsley’s new study supports that idea but it also shows that dreaming while you nap can strengthen our memories even further.

Maze_taskShe asked 99 volunteers to learn the layout of a complex virtual maze so that they could reach a specific landmark after being dropped at a random starting point. Five hours later, they were tested again. Those who had stayed awake in the intervening time beat their previous times by 26 seconds, but those who had had a 90-minute nap improved by a whopping 188 seconds.

But those who dreamt about the task fared even better. Wamsley either asked her recruits directly about whether they dreamt about the labyrinth, or asked them to give an open-ended report of everything that was going through their mind while they were asleep. Either way, those who had thought about the maze during their short nap improved far more than those who didn’t. They also beat those who mentally replayed their training again while awake. These striking results suggest that there’s something special about the mental rehearsals that happen during dreaming sleep.

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Brain-training games get a D at brain-training tests

By Ed Yong | April 20, 2010 1:00 pm

Braintrain.jpgYou don’t have to look very far to find a multi-million pound industry supported by the scantiest of scientific evidence. Take “brain-training”, for example. This fledgling market purports to improve the brain’s abilities through the medium of number problems, Sudoku, anagrams and the like. The idea seems plausible and it has certainly made bestsellers out of games like Dr Kawashima’s Brain Training and Big Brain Academy. But a new study by Adrian Owen from Cambridge University casts doubt on the claims that these games can boost general mental abilities.

Owen recruited 11,430 volunteers through a popular science programme on the BBC called “Bang Goes the Theory”. He asked them to play several online games intended to improve an individual skill, be it reasoning, memory, planning, attention or spatial awareness. After six weeks, with each player training their brains on the games several times per week, Owen found that the games improved performance in the specific task, but not in any others.

That may seem like a victory but it’s a very shallow one. You would naturally expect people who repeatedly practice the same types of tests to eventually become whizzes at them. Indeed, previous studies have found that such improvements do happen. But becoming the Yoda of Sudoku doesn’t necessarily translate into better all-round mental agility and that’s exactly the sort of boost that the brain-training industry purports to provide. According to Owen’s research, it fails.

All of his recruits sat through a quartet of “benchmarking” tests to assess their overall mental skills before the experiment began. The recruits were then split into three groups who spent the next six weeks doing different brain-training tests on the BBC Lab UK website, for at least 10 minutes a day, three times a week. For any UK readers, the results of this study will be shown on BBC One tomorrow night (21 April) on Can You Train Your Brain?

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Amnesiacs show that emotions linger long after memories fade

By Ed Yong | April 13, 2010 8:00 am

Guy-Pearce_MementoI can still remember the details of my wedding day with the most crystalline vividness, from the flower arrangements to the design of the invitations to the contents of my speech. I can also easily recall the sense of elation, hope and fulfilment. These emotional memories are very much fused to my memories of the events themselves, but they aren’t one and the same. A new study suggests that, like everyone else, I recorded these emotional memories independently of the factual aspects of the day.

Typically, the happiness of a wedding day or the sadness of a death becomes inextricably linked to the details of those events, as we repeatedly replay and reflect on them in our heads. To see the true split between an emotional event and the emotions it triggers, you need some very special conditions. Justin Feinstein from the University of Iowa College of Medicine found some – the brains of amnesiac patients.

Feinstein worked with a group of five patients who had a rare condition called anterograde amnesia, the same one that afflicted the protagonist of Memento. All the patients had suffered severe brain damage to both halves of their hippocampus, a part of the brain that’s essential for long-term memory. As a result, they couldn’t form any lasting memories after the point when they sustained their injuries. For the rest of their lives, new facts and experiences are like whispers on a breeze, lingering for moments before vanishing again.

However, it seems that these patients can retain feelings of happiness or sadness long after they’ve forgotten the events that triggered these emotions. Feinstein asked the quintet to watch film clips that either portrayed tragic scenes of loss or death, or comedic scenes of humour and laughter.

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Chimps trump university students at memory task

By Ed Yong | February 24, 2010 12:00 pm

This article is reposted from the old WordPress incarnation of Not Exactly Rocket Science.

Chimps trump university students at memory taskWe humans aren’t used to having our intelligence challenged. Among the animal kingdom, we hold no records for speed, strength or size but our vaunted mental abilities are unparalleled. But research from Kyoto University shows that some chimps have a photographic memory that puts humans to shame.

In 2007, Sana Inoue and Tetsuro Matsuzawa found that young chimps have an ability to memorise details of complex images that is literally super-human. Boffin chimp Ayumu, outperformed university students in memory tasks where they had to rapidly memorise numbers scattered on a touchscreen and press them in numerical order.

This is the first time that an animal has outmatched humans in a mental skill. Recently, I’ve previously blogged about animals that show abilities once considered to be uniquely human, including jays that can plan for the future, rats that know how much they know, armour-wearing octopuses, fable-confirming rooks and premeditating chimps.

But in all these cases, the animals merely showed that they could do similar types of mental feats to us. They never actually challenged our abilities in terms of complexity or scale. Simply put, a crow may be able to combine tools together, but it’s never going to be able to engineer a computer.

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The memory molecules – interview with Todd Sacktor (and a feature in Eureka)

By Ed Yong | January 7, 2010 4:00 am

The latest issue of Eureka, the Times’s monthly science supplement, is out today. I’ve been incredibly supportive of the venture and it’s great to see that a major national newspaper is increasing its science coverage, rather than cutting back on it. For this issue (the fourth, I think), I’ve written a piece on fear and memory, including a lot of research that I’ve previously covered in this blog.

While writing the piece, I interviewed a scientist called Todd Sacktor who’s doing some fascinating work in this field. Sacktor discovered that a protein called PKMzeta is vital for storing memory. Remove it, and memories are deleted, seemingly irreversibly. I’m printing the full transcript of the interview here, as a sort of companion piece to the Eureka feature. Think of it like one of the extras on a DVD.

These are the sorts of services that I think modern journalists can provide for their readers, to expand the boundaries of an article well beyond the first capital and the final fullstop. It won’t work in every case and time is obviously a factor, but there are exceptions when a scientist will be so eloquent and enthusiastic that it would be a crime not to print all of their words. There’s plenty of golden material here that didn’t make it to the final piece because of word limits or because it didn’t fit in the narrative. Here, you’ll hopefully get a fuller picture of PKMzeta. And for non-journalists, it might be interesting to see where I’ve pulled out quotes for the actual piece.

When people think about memory, they often think of discrete things like files on a computer that can be stored or lost. How do such metaphors stand now?

We think memories are stored by the action of PKMzeta at specific synapses. So the commonplace notion of files on a computer hard disk isn’t that far from the truth now. In a sense, it’s actually closer than the old neuroscientific explanation – that you have the growth of new synapses that, once grown, simply connect networks of neurons more strongly. It’s a bit like branches of a tree getting thicker or denser and that’s the memory – they are are now stronger because of these new physical connections. 

But a computer hard disk, the structure is there. The hard disk has a certain size and certain places for the zeroes and ones, but you can store different information in the pattern of zeroes and ones. PKMzeta shows that it’s kind of a mix between these two notions. PKMzeta turns up at specific synapses after you learn something. The unique properties of this enzyme allow it to be active all the time (which is really unusual) and active at specific synapses, doubling the strength of those connections rather than their number. A synapse with PKMzeta is twice as strong as it otherwise would be.

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Rewriting fearful memories by bringing them back to mind

By Ed Yong | December 9, 2009 1:00 pm

Bringing an old memory back to mind would, you might think, strengthen it. But not so – when memories are recalled, they enter a surprisingly vulnerable state, when they can be reshaped or even rewritten. It takes a while for the memory to become strengthened anew, through a process called reconsolidation. Memories aren’t just written once, but every time we remember them.

This system allows us to rapidly update our memories with new information, for a more flexible and adaptable brain. It also means that the very act of remembering provides a valuable window of opportunity, during which memory can be manipulated. Now, a group of US scientists have done just that, exploiting this window to remove a simple fearful memory using fresh information, rather than drugs or invasive surgery.

Daniela Schiller from New York University trained volunteers to fear a coloured square by pairing it with a mild electric shock (the “acquisition” part of the graph below). The next day, Schiller reactivated their fear memories by once again showing them the shocking squares. When they did, their skin betrayed their nervousness by becoming better at conducting electricity, a sure sign that they were sweating.

Schiller then tried to extinguish their fearful responses with “extinction trials”, where they repeatedly saw the square without any shocks. This procedure ought to break the first day’s conditioning and it did temporarily (the “extinction” part of the graph below). But fear memories are harder to banish than that. On the third day, the volunteers were once again exposed to the scary squares, which, once again, sent most of them into a nervous sweat (the “re-extinction” part).

The only exceptions were the people whose memories of their conditioning had been reactivated 10 minutes before they went through the extinction training. If Schiller left a gap of 6 hours, or if she took the recruits straight into the extinction trials, they still reacted nervously to the squares. These results fit with the idea of reconsolidation, where remembering a memory provides a short window of opportunity for overwriting it. Doing so produces an anti-fear blockade that lasts much longer than 24 hours.

Schiller invited her volunteers back a year later, and 19 out of 65 returned. She gave them four shocks and showed them the coloured squares again – a powerful procedure that should have dramatically reinstated the fears they had been conditioned with a year before. But those whose fear memories had been overwritten didn’t succumb, while volunteers who previously belonged to the 6-hour or the no-reminder groups quickly started to get nervous again.

Best of all, Schiller found that the effect of the fear blockade was very specific. In a second experiment, she paired two squares of different colours (CSa and CSb in the graph below) with electric shocks. But she only reminded her volunteers about one of them before trying to wipe their fears away. And as predicted, a day later, only the fear memory that had been reactivated had been eventually blocked. While this is a fairly simplistic scenario, the specific nature of the effect is a must if any realistic application is to come of this one day. In real life, scary memories are associated with many possible triggers and not just coloured squares.

This study is a sequel. Earlier this year, Joseph Le Doux, whose lab Schiller works in, published similar results showing that the same technique was successful in rats. They conditioned rats to link a tone with electric shocks and then erased that memory in the same way that they did for the human volunteers – they reminded the rats of the tone to open the reconsolidation window, and then used the time to overwrite their conditioning using a shock-free tone. As with humans, the timing was crucial.

Other studies have used drugs to the same ends but many of these have been toxic. The only promising drug, the beta-blocker propanolol, was the star of a media circus earlier this year. Merel Kindt showed that propanolol could erase the emotional sting of a fearful memory. The research exploited reconsolidation windows, just as Schiller’s study did. By giving propanolol to people before they recalled a scary spider memory, Kindt could erase the fearful response it triggered.

Schiller says that it would be better to use methods that don’t involve drugs because of any potential side effects. But Kindt isn’t entirely convinced by these new experiments. She told me that a person’s sweaty skin tells you about whether they expect something bad to happen but not whether they’re afraid of it. In her experiment, she measured fearful responses by looking at the startle reflex – how strongly people blink to the terror in question.

Schiller may have more work to do to convince her critics but, at the very least, her study provides more evidence that reconsolidation is something that could be manipulated to treat anxiety disorders or PTSD. Drugs don’t have to be the solution – earlier this year, British researchers showed that playing Tetris can stop traumatic memories from consolidating in the first place. Perhaps the famously addictive game could be used to interfere with reconsolidation too.

Ironically enough, studies like these often provoke fear and panic that they will fall into the wrong hands. Outraged editorials often follow, chiding us that fearful memories are useful things to have because they remind us not to poke that tiger or touch that flame. Indeed, there’s evidence that our brain actively protects such memories, shielding them in a net of guardian molecules. Manipulating such systems is to play God with people’s mind.

But such criticisms miss the point. For a start, the benefits of remembering fearful experiences can often lead to the extreme drawbacks of anxiety or post-traumatic stress disorder. But perhaps most importantly, the entire point of reconsolidation is to allow the brain to incorporate new data into its existing framework. All these studies are doing is to give it the right information at the right time, nothing more than an advert or a classroom seeks to do.

Reference: Nature doi:10.1038/nature08637

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Memories can be strengthened while we sleep by providing the right triggers

By Ed Yong | November 20, 2009 9:20 am

In my final year of university, with exam deadlines looming and time increasingly fleeting, I considered recording some of my notes and playing them over while I was asleep. The concept of effectively gaining 6 extra hours of revision was appealing, but the idea didn’t stick – it took too long to record the information and the noise stopped me from sleeping in the first place. And the whole thing had a vague hint of daftness about it. But a new experiment suggests that the idea actually has some merit, showing that you can indeed strengthen individual memories by reactivating them as you snooze.

Sleep is a boon to newborn memories. Several experiments have shown that sleep can act as a mental cement that consolidates fragile memories into stable ones. But John Rudoy from Northwestern University wanted to see if this process could be taken even further by replaying newly learned information while people slept.

He asked a dozen volunteers to remember the positions of 50 different objects as they appeared on a screen. The items, from kittens to kettles, were all accompanied by a relevant noise, like a meow or a whistle. Shortly after, the recruits all had a short nap. As they slept, Rudoy played them the sounds for 25 of the objects, against a background of white noise. When the volunteers woke up, they had to place each of the 50 objects in the right position, and they were marked on how close they came to the actual target.

The results were very clear – the volunteers positioned the objects around 15% more accurately if they’d heard the relevant sounds while they slept. Although the sleep sounds didn’t work for everyone, the majority of the participants – 10 out of 12 – benefited in some way. And none of them knew they heard anything at all while they slept. When they were told this and asked to guess which sounds they heard, they didn’t do any better than chance.  

Sleep_memory.jpg

To show that this isn’t just a general benefit of revision, whether conscious or not, Rudoy did a similar experiment. This time, his volunteers heard the noises after they had first seen the objects but while they were still awake. This group proved to be no better at remembering the items’ locations than those who didn’t hear the second round of sounds.

Finally, to understand what was going on in the brains of the slumbering recruits, Rudoy used electroencephalograms (EEG) to measure the electrical activity in the heads of 12 fresh volunteers. He showed that people who were better at remembering the objects’ positions after their nap were also those who showed the most brain activity when they heard the sounds Rudoy thinks that hearing the sounds during sleep prompted the brain to rehearse and strengthen associations between the objects and their locations.

Some people think that sleep improves memories in a general way, by making our brains more flexible and easing the incorporation of new information. But these simple experiments show that the benefits can be very specific indeed. It’s not only possible to strengthen specific and individual memories by providing the right triggers, but we get the opportunity to do so every single night.

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Even without practice, sleep improves memory of movements

By Ed Yong | November 4, 2009 8:30 am

When we think of memory aids, we consider repeating what we’ve learned, using clever mnemonics, or breaking information down into bite-size chunks. But one of the best memory aids we have available to us is something we all do on a daily basis – sleep. Studies have found that sleep enhances our memories of facts and physical skills alike. It can even help us remember movements that we see others do.

But this only works within a short window. Ysbrand van der Werf from the Netherlands Institute of Neuroscience found that people who saw a video of someone tapping keys on a laptop remembered the sequence more accurately if they slept on it within 12 hours. Any longer than that, and the snoozing didn’t boost their recall.

Van der Werf showed the video to 128 volunteers and then tested them on either the same finger-tapping sequence or a different one. The gap between video and test was either 12 or 24 hours, and some of the volunteers were allowed to sleep during the interval while others were not.

If the test sequence didn’t match the ones they saw, all the recruits did equally well. But if the sequence was the same, those who managed to sleep within the first 12 hours stood out – they were 22% faster and made 42% fewer errors than their peers who either didn’t sleep or who slept later. They even improved whether they had their naps during the day or in the evening.

These results parallel those from experiments where people actually had a chance to practice new skills before their naps. The big difference here is that the improvements came only after watching movements rather than actually performing them.

Van der Werf confirmed that by taking great care to ensure that his volunteers weren’t actually trying out the keystrokes for themselves. While watching the video, they had to tap two different keys to keep their fingers busy. Van der Werf even measured the muscle activity in the arms of seven volunteers to rule out the possibility that they were making subtle, unnoticed finger movements.

If it’s not to do with practice, it’s not to do with memorising the digits themselves or the position of the keys either. If the volunteers just saw the numbers flash up on screen, or if they saw coloured squares light up in the same position as the relevant keys, they didn’t become more accurate or faster when they had to replicate the sequence. They needed to actually see someone else doing it.

Van der Werf thinks that the recruits probably imagined their finger movements while watching the video, even if they didn’t actually try them out. It may even involve the mirror neurons that fire when an individual performs an action and when it sees someone else doing the same action (although mirror neurons have only been properly found in monkeys, and not humans). 

Either way, the results highlight the importance of a good sleep when people are trying to pick up new physical skills. This could be especially important for people who can’t possibly to practice the movements in question, such as those who have suffered a stroke or broken a limb. And clearly the most important implication is that the next time I see someone doing parkour, I will immediately lie down and have a little nap. When I wake up, I will be Batman. SCIENCE!

Reference: PNAS doi:10.1073_pnas.0901320106

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MORE ABOUT: Memory, Sleep
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