Awaiting a theory of neural weather

In a recent New York Times editorial, psychologist Gary Marcus noted that neuroscience is still awaiting a ‘bridging’ theory that elegantly connects neuroscience with psychology.

This reflects a common belief in cognitive science that there is a ‘missing law’ to be discovered that will tell us how mind and brain are linked – but it is quite possible there just isn’t one to be discovered.

Marcus, not arguing for the theory himself, describes it when he writes:

What we are really looking for is a bridge, some way of connecting two separate scientific languages — those of neuroscience and psychology.

Such bridges don’t come easily or often, maybe once in a generation, but when they do arrive, they can change everything. An example is the discovery of DNA, which allowed us to understand how genetic information could be represented and replicated in a physical structure. In one stroke, this bridge transformed biology from a mystery — in which the physical basis of life was almost entirely unknown — into a tractable if challenging set of problems, such as sequencing genes, working out the proteins that they encode and discerning the circumstances that govern their distribution in the body.

Neuroscience awaits a similar breakthrough. We know that there must be some lawful relation between assemblies of neurons and the elements of thought, but we are currently at a loss to describe those laws.

The idea of a DNA-like missing component that will allow us to connect theories of psychology and neuroscience is an attractive one, but it is equally as likely that the connection between mind and brain is more like the relationship between molecular interactions and the weather.

In this case, there is no ‘special theory’ that connects weather to molecules because different atmospheric phenomena are understood in multiple ways and across multiple models, each of which has a differing relationship to the scale at which the physical data is understood – fluid flows, as statistical models, atomic interactions and so on.

In explanatory terms, ‘psychology’ is probably a lot like the weather. The idea of their being a ‘psychological level’ is a human concept and its conceptual components won’t neatly relate to neural function in a uniform way.

Some functions will have much more direct relationships – like basic sensory information and its representation in the brain’s ‘sensotopic maps’. A good example might be how visual information in space is represented in an equivalent retinotopic map in the brain.

Other functions will have more more indirect relationships but in great part because of how we define ‘functions’. Some have very empirical definitions – take iconic memory – whereas others will be cultural or folk concepts – think vicarious embarrassment or nostalgia.

So it’s unlikely we’re going to find an all-purpose theoretical bridge to connect psychology and neuroscience. Instead, we’ll probably end up with what Kenneth Kendler calls ‘patchy reductionism’ – making pragmatic links between mind and brain where possible using a variety of theories and descriptions.

A search for a general ‘bridging theory’ may be a fruitless one.
 

Link to NYT piece ‘The Trouble With Brain Science’.

Out on a limb too many

Two neuropsychologists have written a fascinating review article about the desire to amputate a perfectly healthy limb known variously as apotemnophilia, xenomelia or body integrity identity disorder

The article is published in the Journal of Neuropsychiatric Disease and Treatment although some who have these desires would probably disagree that it is a disease or disorder and are more likely to compare it to something akin to being transgender.

The article also discusses the two main themes in the research literature: an association with sexual fetish for limb aputation (most associated with the use of the name apotemnophilia) and an alteration in body image linked to differences in the function of the parietal lobe in the brain (most associated with the use of the name xenomelia).

It’s a fascinating review of what we know about this under-recognised form of human experience but it also has an interesting snippet about how this desire first came to light not in the scientific literature, but in the letters page of Penthouse magazine:

A first description of this condition traces back to a series of letters published in 1972 in the magazine Penthouse. These letters were from erotically-obsessed persons who wanted to become amputees themselves. However, the first scientific report of this desire only appeared in 1977: Money et al described two cases who had intense desire toward amputation of a healthy limb. Another milestone was a 2005 study by Michael First, an American psychiatrist, who published the first systematic attempt to describe individuals who desire amputation of a healthy limb. Thanks to this survey, which included 52 volunteers, a number of key features of the condition are identified: gender prevalence (most individuals are men), side preference (left-sided amputations are most frequently desired), and finally, a preference toward amputation of the leg versus the arm.

The review also discusses a potentially related experience which has recently been reported – the desire to be paralysed.

If you want a more journalistic account, Matter published an extensive piece on the condition last year.
 

Link to scientific review article on apotemnophilia / xenomelia.
Link to Matter article.

A reality rabbit-hole from the dream world

I’ve got an article in The Observer about how the science of lucid dreaming is being pushed forward by the development of ‘in-dream’ experiments.

A lucid dream is where you become aware you are dreaming and where you can potentially change elements of the dream as it happens.

The piece discusses how eye movements allow communication from within dreams to researchers in the sleep lab and how this has led to studies involving people doing experimental tasks in the dream world.

One of our most mysterious and intriguing states of consciousness is the dream. We lose consciousness when we enter the deep waters of sleep, only to regain it as we emerge into a series of uncanny private realities. These air pockets of inner experience have been difficult for psychologists to study scientifically and, as a result, researchers have mostly resorted to measuring brain activity as the sleeper lies passive. But interest has recently returned to a technique that allows real-time communication from within the dream world.

The article also touches on the ‘dream hacking’ community who borrow from the scientific literature to try an increase their chances of having a lucid dream, sometimes using psychiatric medication for which vivid dreams are considered a side-effect.

The full piece is at the link below.
 

Link to article in The Observer.

Research Digest post #2

My time in the BPS Research Digest hotseat continues. Today’s post is about a lovely study by Stuart Ritchie and colleagues which uses a unique dataset to look at the effect of alcohol on cognitive function across the lifespan. Here’s the intro:

The cognitive cost or benefit of booze depends on your genes, suggests a new study which uses a unique longitudinal data set.

Inside the laboratory psychologists use a control group to isolate the effects of specific variables. But many important real world problems can’t be captured in the lab. Ageing is a good example: if we want to know what predicts a healthy old age, running experiments is difficult, even if only for the reason that they take a lifetime to get the results. Questions about potentially harmful substances are another good example: if we suspect something may be harmful we can hardly give it to half of a group of volunteer participants. The question of the long-term effects of alcohol consumption on cognitive ability combines both of these difficulties.

You can read the rest here: Alcohol could have cognitive benefits – depending on your genes.

See also, Tuesday’s post: A self-fulfilling fallacy?

Detecting inner consciousness

CC Licensed photo by Flickr user hernán. Click for source.Mosaic has an excellent in-depth article on researchers who are trying to detect signs of consciousness in patients who have fallen into coma-like states.

The piece meshes the work of neuroscientists Adrian Owen, Nicholas Schiff and Steven Laureys who are independently looking at how to detect signs of consciousness in unresponsive brain-injured patients.

It’s an excellent piece and communicates the key difference between various states of poor response after brain injury that are crucial for making sense of the ‘consciousness in coma’ headlines.

One of the key concepts is the minimally conscious state which is where patients show signs of fleeting and impaired consciousness but which is nonetheless verifiably present.

However, MCS is still a very impaired state to be in and this is sometimes missed by news reports.

For example, lots of coverage of a recent Lancet study suggested that ‘one third of patients in persistent vegetative state (a state with no reliable signs of consciousness) may be conscious’ as if this meant they were fully conscious but trapped in their bodies, when actually they just reached criteria for minimally conscious state.

My only point of contention with the Mosaic article is that it’s a little too enthusiastic about sleeping pill zolpidem, which has been reported to lead to a ‘miraculous’ recovery in some case reports but where results from early systematic studies still look bleak.

Nevertheless, an excellent piece that’s probably one of the best accounts of this important and innovative area of research you’re likely to read for a long-time.
 

Link to Mosaic article ‘The Mind Readers’.

Coma alarm dreams

Intensive Care Medicine has published a wonderfully written and vivid account from a teenager who spent time brain injured and hallucinating in an intensive care unit.

The writer describes how he was admitted to intensive care at the age of 15 after suffering a head injury and had intense and bizarre hallucinations which are, as we know now, surprisingly common in critical care patients.

My experience of the time under sedation can be split into two. There was what I could perceive of the real world around me, and then there was my dream world.

In the real world, the most constant feature was sound. I could hear the nurses talking, understanding everything they said. They always spoke their names. They were always kind, conscious I think that I might hear them. They helped me to relax. I could hear the noises of the ward, tones of voices and alarms. The alarms made me tense. I can remember Mum talking to me a lot and Dad reading me ‘The Hobbit’, although I still can’t remember the names of all the dwarves. Mum and Dad’s voices always came from the left.

My other senses were not wholly switched off either. Things were put in my mouth: tubes, sucky things, wet watery pads and a toothbrush. Someone moved my hair about. I felt furry and silky toys placed under my fingers. My brother and sisters had brought a knitted tortoise and a horse for me. My feet were moved about and stretched, which felt really good. I remember that the rolled-up bed sheets were uncomfortable.

Other sensations were less good. The constant, repetitive shining of a bright light in my remaining eye really annoyed me – I am sure I can remember every single time.

Then there was my dreaming. I lived in the dream world nearly all the time and it went on and on. The dreams were vivid, terrifying and very disturbing. There were some good ones but unfortunately for me a lot of really bad ones. I can still remember most of them even now, more than a year since.

At the sound of an alarm, a giant monster appeared with a meat cleaver and pursued me around the sports hall. I had to protect a girl and prevent an army from crossing a river. The whole river and hall were aflame. I was burning from the heat.

In another I had to stop an alarm-driven colossal centipede from crossing a bridge. I could see the shadow of monsters looming towards me behind a curtain. I knew the monsters were there and about to consume me, but I lay transfixed, unable to move, and I remember feeling myself sweating with excruciating fear. I was then on the bridge of a nuclear submarine with maniacs trying to blow up the world, there was a huge explosion. Then it ended.

I was aboard a flying craft. I was there to stop green-coated aliens from creating human missiles. The aliens were forcing people into missile tubes. They were going to drop the human bombs from the aircraft.

Then there was a shape-shifter leopard beast chasing me and my friends. We were working in a fast-food place on a ship. It cornered us, and the Kentucky Fried Chicken sign burst into red lightning.

But I knew when something really nasty was going to happen. I could always hear the same alarm going off. It was a signal for the monsters to appear, for the centipede to attack, for bombs to be dropped, I would be sacrificed…I was very afraid. Tension would build to some hideous climax. Looking back, I suspect the pressure in my brain was causing both the nightmares and the alarm to go off.

I have made a great recovery from my injuries due in large part to the excellent care that was taken of my brain in intensive care. I have been into see the team a few times but I never stay too long. Those alarms still make me feel nervous!

As I noted in a recent article, these sorts of hallucinations were thought to be a distressing but ultimately irrelevant part of recovery but more recent studies suggests that have longer-term psychological impact that can be problematic in its own right.
 

Link to locked article ‘Coma alarm dreams on paediatric intensive care’

Bomb disposal for the brain

New Statesman has an excellent profile of the wise, funny and acerbic neurosurgeon Henry Marsh.

Marsh was the subject of the fantastic 2007 documentary The English Surgeon but he’s now one year away from retirement and has clearly decided that diplomatic responses are no longer a tactical necessity.

The piece also gives a vivid insight into the working life and daily challenges of a consultant neurosurgeon.

It’s also wonderfully written. This is pure joy:

When he finally went to medical school, at the Royal Free Hospital in London, he wasn’t sure about his choice. “I thought medicine was very boring,” he says bluntly. Henry is not a man to refrain from speaking his mind. “I didn’t like doctors. I didn’t like surgeons. It all seemed a bit dumb to me.” In Do No Harm he writes of his revulsion at what much surgery generally entails: “long bloody incisions and the handling of large and slippery body parts”.

But while working as a senior house officer, he observed a neurosurgeon use an operating microscope to clip off an aneurysm – a small, balloon-like blowout on the cerebral arteries that can cause catastrophic haemorrhages. It is intensely delicate work, using microscopic instruments to manipulate blood vessels just a few millimetres in diameter. It is also, as Henry says, like bomb disposal work, in that it can go very badly wrong – with the crucial difference that it is only the patient’s life at risk, not the surgeon’s. If this or any other kind of serious neurosurgery goes right, however, the doctor is a hero. “Neurosurgery,” he smiles, “appealed to my sense of glory and self-importance.”

Marsh has just written an autobiography called Do No Harm which I’ve just started reading. I’m only part way through but it’s already gripping and wonderfully indiscreet.
 

Link to New Statesman profile of Henry Marsh.