Category: Inside the Brain

Implanted electrode grids are used to record brain activity in people who need neurosurgery – a technique known as electrocorticography.

But rather than just ‘reading’ from the brain, neuroscientists are starting to use them to ‘write’ to the brain, to the point of being able to temporarily simulate specific brain disorders for experimental studies.

This is the subject of my latest Observer column which looks at the history of open-brain stimulation studies and covers recent research by a joint British – Japanese team which has been using the grids to temporarily simulate a form of brain disorder called ‘semantic dementia’ in live volunteers.

The precision is such that the Lambon Ralph team and a team at Kyoto University Medical School, led by Riki Matsumoto, have used an implanted grid to temporarily simulate characteristics of a brain disease called semantic dementia. Like Alzheimer’s, semantic dementia is a degenerative disorder, but one in which brain cells that specifically support our understanding of meaning rapidly decline. Studies of patients with semantic dementia have taught us a great deal about how memory is organised in the brain but the disorder is swift and unpredictable, and a method that can mimic the effects while recording directly from the cortex is a powerful tool.

To be clear, the grids are not installed for this purpose. They’re installed because they are part of brain surgery to treat otherwise untreatable epilepsy. The grids allow neurosurgeons to locate the exact bit of the brain that triggers seizures so it can be removed.

The article is in part a coverage of the amazing neuroscience, from 1886 to the present day, and in part a tribute to the neurosurgery patients who have volunteered to help us understand the brain.
 

Link to Observer article.

I’ve just found a short but interesting study on Psalm 137 and how it likely has one of the first descriptions of brain damage after stroke.

The Psalm is still widely sung but it has some particular lines which made the researchers take notice. Here they are in modern English from the New International Version of the bible:

If I forget you, Jerusalem,
  may my right hand forget its skill.
May my tongue cling to the roof of my mouth
  if I do not remember you,
if I do not consider Jerusalem
  my highest joy.

This seems to describe some clear physical symptoms but the bible has numerous versions all of which have different translations and even in their early versions do not always agree on the exact wording.

As a result the researchers looked at Spanish, English, German, Dutch, Russian, Greek, and Hebrew versions to examine the consistency of the text and the variations in description of these curious physical effects. The combined description includes:

If I forget of you, oh Jerusalem, my right hand (my right side) shall dry, be paralyzed, loose its ability, its dexterity… That my tongue shall stick (shall be weakened, arrested) to my palate (in my throat), if I remember you, if I do not permit Jerusalem to be my greatest joy (if I do not sing of Jerusalem as my greatest joy)

Both right-sided paralysis and loss of expressive speech are clear symptoms of a stroke of the left middle cerebral artery, where the blood flow is blocked – leading to the death of the surrounding brain tissue, suggesting that the Psalm may be wishing these effects on people who forget the importance of Jerusalem.

The powerful nature of the wish is perhaps explained by the fact that the Psalm is widely believed to have been written as a lament by Jewish people exiled after the conquest of Jerusalem by the Babylonians in 586 BCE.

But why these specific symptoms are mentioned may have more to do with ancient beliefs about stroke itself.

The reason the condition is still called stroke is because people originally believed that it was a result of being ‘struck down’ by God.

The Psalm still remains popular and the opening lines “By the rivers of Babylon…” have spawned a cottage industry in bad pop songs most of which miss out the lines concerning stroke.

However, the track Jerusalem by Jewish reggae hip-hop maestro Matisyahu does focus on this part of the Psalm, which he mashes-up along with lyrics from Matthew Wilder’s Break My Stride.
 

Link to study on the neurology of Psalm 137.
Link to Jerusalem by Matisyahu.

A study presented at the recent Usenix conference demonstrated how it is possible to get private information from the brains of people who use commercial brain-computer interfaces – like NeuroSky and Emotiv.

These headsets are designed for gamers and are cheaper, less accurate versions of EEG devices – used by scientists to read the electrical activity of the brain by attaching electrodes to the surface of the scalp.

The new study, titled ‘On the Feasibility of Side-Channel Attacks with Brain-Computer Interfaces’ (available online as a pdf), took advantage of a reliable brain signal called the P300.

The P300 reflects the brain’s categorisation of something as relevant, important or meaningful. If you’re shown a series of photo portraits, for example, the P300 will kick in when you see photos of people you recognise but not to strangers.

One form of the not-very-reliable EEG ‘lie detector’ is based on this principle. Called the Guilty Knowledge Test, the idea is that the police would show you photos of the crime scene, and if you had actually been there, your P300 would kick in.

This new study was based on a similar principle. The researchers ran various experiments based on the same idea: they’d ask a question to make sure the key information was at the forefront of the study participant’s mind, and then they’d fire a bunch of information at the volunteer to pick out which was most associated with the P300.

For example, in one experiment participants were told they would have to type in the first digit of their newly acquired PIN number into the computer, but before this happened, the volunteers were shown a series of single digits, while the software recorded which numerals were most associated with the P300.

In another, the P300 was recorded while participants were shown pictures of branded credit cards and bank machines. Another experiment asked participants to think of their month of birth before showing them all the options, while another flashed up maps of the local area to determine their approximate home address.

You can see how the researchers were angling to get the equivalent of essential account details out of the volunteers.

Although the set-up was a little artificial, the researchers note that this sort of unconscious personal detail dredging could be incorporated into a game-like activity, so people would be unaware of what was really happening.

The test was a success scientifically, in that the key information was identified more often than chance, but fraudsters are unlikely to be eschewing email hacking for NeuroSky pwning anytime soon. The hit rate was about 10-20%.

Nevertheless, as a demonstration of a ‘hacking brain wave data from a commercial gaming equipment to get personal information’ you have to take your hat off to the research team.

Even more interestingly, perhaps, is the increasing trend for security technology to move towards the interface between mind and machine.

Another study presented at the same conference showed how people could input ‘passwords’ into a system without any conscious knowledge of knowing a password.

The idea relies on implicit learning – which is where you learn connections between things without having any conscious knowledge of doing so.

For example, when playing a computer game like Guitar Hero or Dance Dance Revolution, the same short sequence of moves might come up several times but you might not be aware of it, because they would be embedded within a larger sequence.

However, simply by having encountered the sequence before you will do better the second time – because you have practised the response – even if you have no conscious memory of it.

For each user, this new study embedded a newly generated ‘password of moves’ several times into a longer sequence and made sure they were well practised. Later, the software could identify each user by spitting out those moves again and checking the performance to see if they’d been encountered before. The participants were unaware of anything except that they were playing a game.

Looking at the bigger picture, the fact that computer security could rely on the fine detail of how the brain works could open up a whole new arena of security vulnerabilities.

Perhaps you could be covertly trained to enter someone else’s security details, or perhaps that last game you played actually trained you to leak your login details in another activity – all of which may be completely unnoticeable to your conscious mind.

Black hat neuroscientists may suddenly become very concerned with how these automatic effects could be influenced in very specific, and of course, very lucrative, ways.
 

Link to study on brain-based personal details hacking (via BoingBoing)
Link to unconscious password study.

The latest issue of The Psychologist has a fascinating article on why time can seem distorted after taking drugs.

The piece is by psychologists Ruth Ogden and Cathy Montgomery who both research the effects of drugs, legal and illegal, on the mind and brain.

The consumption of drugs and alcohol has long been known to warp time experiences. In his much-quoted book Confessions of an English Opium Eater, Thomas De Quincey (1821/1971) noted that opium intoxication resulted in distortions to the passage of time to the extent that he ‘Sometimes seemed to have lived for 70 or 100 years in one night; nay, sometimes had feelings representative of a millennium passed in that time’.

Similar experiences were also reported by Aldous Huxley (1954) in Doors of Perception after consuming mescaline and LSD. Drug-induced distortions to time are not only experienced by renowned literary figures: a quick search of an internet drug forum will reveal that many drug users report similar experiences to De Quincey and Huxley following marijuana, cocaine and alcohol use.

The article notes that both the social context in which drugs are taken (e.g. drinking on a night out) and the pharmacological effects of the substances can each add their own ingredients to the time stretching or shrinking effects.
 

Link to article ‘High Time’ in The Psychologist.

I’ve got an article in today’s Observer about the re-emergence of hypnosis into the scientific mainstream despite the fact that the technique is still associated with stereotypes.

The piece has been oddly titled ‘hypnosis is no laughing matter’, which kind of misses the point, because no-one laughs at it, but many scientists do find it uncomfortable because of its long-running associations with stage shows, high-street hypnotists and the like.

The sub-heading also suggests that the article is about the revival of hypnosis as a ‘clinical tool’ when the article only discusses the use of hypnosis in the lab.

However, get past the headings and the piece discusses the genuinely interesting cognitive science of hypnosis and suggestibility.

The recent research is interesting not so much because we are learning about hypnosis itself, but because it is helping us understand some quite striking things about the fundamentals of the mind.

Amir Raz and colleagues at McGill University in Montreal reported that it was possible to “switch off” automatic word reading and abolish the Stroop effect – a psychological phenomenon that demonstrates a conflict between meanings, such as where we are much slower to identify the ink colour of a word when the word itself describes a different hue. Furthermore, when this experiment was run in a brain scanner, participants showed much lower activation in both the anterior cingulate cortex, an area known to be particularly involved in resolving conflict between competing demands, and the visual cortex, which is crucial for recognising words. Although this may seem like a technicality, to the scientific world it was a strikingly persuasive demonstration that hypnosis could apparently disassemble an automatic and well-established psychological effect in a manner consistent with the brain processes that support it.

One of the other exciting areas is the use of hypnosis to temporarily induce altered states of consciousness that can then be studied in the lab. More of that in the article.
 

Link to Observer article.

TED have a fantastic animation that explains how pain works and how it is relieved by two common analgesics – aspirin and ibuprofen.

Of course, pain relievers work in many different ways – the opioids, for example, are vastly different – but the four-minute video is a wonderful guide to the neuroscience of two common household pills.

Excellent stuff.
 

Link to ‘How Do Pain Relievers Work?’ (via @brainpicker)

The June issue of the neuroscience journal Brain has an amazing cover showing “increasingly bizarre and menacing caricatures by an artist with frontotemporal lobar degeneration during the course of his illness”.

The caption reads:

From left, the first picture drawn many years before his illness; the middle pair in the first 2 years of dementia; and that on the right at least 3 years into the illness. Background: Gouache entitled ‘Unravelling Boléro’, showing de novo transmodal creativity comprising auditory to visual transformation, by a patient with primary progressive aphasia…

 

Link to Brain cover (via @tiempoasm)

A couple of online articles have discussed whether you would be conscious of being shot in the head with the general conclusion that it is unlikely because the damage happens faster than the brain can register a conscious sensation.

While this may be true in some instances it ignores that fact that there are many ways of taking a bullet to the head.

This is studied by a field called wound ballistics and, unsurprisingly when you think about it, the wound ballistics of the head are somewhat special.

Firstly, if you get shot in the head, in this day and age, you have, on average, about a 50/50 chance of surviving. In other words, it’s important to note that not everyone dies from their injuries.

But it’s also important to note that not every bullet wound will necessarily damage brain areas essential for consciousness.

The image on the top left of this post charts the position of fatal gunshot wounds recorded in soldiers and was published in a recent study on combat fatalities.

For many reasons, including body armour and confrontation type, head wounds to soldiers are not necessary a good guide to how these will pan out in civilians, but you can see that there are many possibilities with regard to which brain areas could be affected.

In fact, you can see differences in the effect of gunshots to the head more directly from the data from Glasgow Coma Scale (GCS) ratings. A sizeable minority are conscious when they first see someone from the trauma team.

It’s also worth noting that deaths are not necessarily due to brain damage per se, blood loss is also a key factor.

An average male has about 6 litres of blood and his internal carotid artery clears about a quarter of a litre per minute at rest to supply the brain. When in a stressful situation, like, for example, being shot, that output can double.

If we need to lose about 20% of our blood to lose consciousness, our notional male could black out in just over two minutes just through having damage to his carotid. However, that’s two minutes of waiting if he’s not been knocked unconscious by the impact.

But if we’re thinking about brain damage, the extent depends on a whole range of ballistic factors – the velocity, shape, size and make-up of the bullet being key.

As it turns out, the brain needs special consideration, not least because it is encased in the skull.

One of the first things to consider is that the skull can fracture and how the fragments themselves can become missiles. In 42 cases of civilian gunshot wounds to the brain two neurosurgeons were able to find bone chips in 16 patients’ brains simply by “digital palpation” – which is a complicated medical term for sticking your fingers in and wiggling them about.

In other words, a shot to one part of the head may have knock-on effects purely due to skull shattering.

However, the skull also sets up a unique target due to its enclosed nature. If someone gets shot in the leg the pressure of the impact can be released into the surroundings. If a bullet gets into the brain the options are fewer because the pressure waves and, indeed, the brain, are largely trapped inside a solid box of bone.

If you want to get an idea of the sorts of pressures involved, just catch a video or two of bullets being fired into ballistic gel and think what would happen if the gel was trapped inside a personally important life-sustaining box.

In fact, if the shot is powerful enough, from high velocity rifles for example, there is a combination of the initial impact and an ‘explosive’ effect which can do substantial damage through forcing the brain to the side of the skull and fracturing from the inside out.

There is one rare effect, called the Krönlein shot, where a high powered shot messily opens the skull but neatly ejects the whole brain on the ground. You can find pictures on the web from pathology articles but, I warn you, they’re neither child friendly nor particularly good tea-time viewing.

Small low-velocity rounds can do quite local damage, however, and despite the tragedy of being shot, we have learnt a surprising amount from people who have survived such wounds.

As we’ve discussed previously, the use of small bore low-velocity bullets during World War I meant that more than ever before and, perhaps since, soldiers survived with small localised brain injuries.

This meant doctors could do some of the first systematic studies into how specific brain areas related to specific functions, based on tests of what brain-injured soldiers could no longer do.

But while it’s true to say that many people will lose consciousness before they even know they’ve been shot, it’s not guaranteed. Although it will mean that some people will be unfortunately aware of their death, it also means that others are able to save themselves.