Month: October 2009

There are a couple of excellent posts on Neurophilosophy covering recent studies that demonstrate the powerful effect of vision on the perception of physical sensations in our body.

The first covers an interesting study that found that looking directly at your hand reduces laser-induced pain compared to a condition where you are only looking at a visual substitute created with a mirror reflection of the other hand (akin to a mirror box set up).

The second post discusses the possibilities of taking advantage of the ‘rubber hand illusion‘ to allow us to feel like we’re physically inhabiting virtual bodies.

Numerous experiments have shown that we look at a rubber hand being touched simultaneously and in the same way as our real hand, the sensation seems to be located in the fake.

This new experiment attempted something similar but in virtual reality, demonstrating that a synchronised ‘touch’ could be perceived as arising from an avatar hand in a 3D computer generated environment.

While the same research team had demonstrated this effect before this new study showed how the effect could transfer, albeit more weakly, to a virtual arm controlled by a brain-computer interface driven solely from EEG readings.

Both of these studies demonstrate how vision is integrated with tactile information from the body to create our sense of body image, ownership and sensation and both get a great write-up from Neurophilosophy.

Link to Neurophilosophy post visual pain reduction.
Link to Neurophilosophy on the ‘virtual hand illusion’.

New Scientist has a fantastic issue on ‘strange journeys of the mind’ that has three great articles on the twilight zone of sleep, simulating psychopathology with hypnosis and laboratory-induced out-of-body experiences.

The piece on the hypnotic simulation of brain disturbances is fantastic, not least because it features two researchers I work with, Peter Halligan and David Oakley, who have done some of the seminal work in the area.

Essentially, the approach views hypnosis as a tool that allows researchers, with the co-operation of the participant, to temporarily alter mental states in a completely safe and reversible way.

Importantly, these alterations, such as blindness or paralysis, seem like they’re happening ‘on their own’ – which helps us understand conditions like conversion disorder, where these sorts of symptoms appear without any neurological damage but without the patient seeming to have any control over them.

The other article which blew me away was on recent studies suggesting that sleep and alertness are not two distinct states of consciousness and in some people with a dementia-like brain disorder the boundaries between sleep and wakefulness completely break down.

That this can happen contradicts the way we usually think about sleep, but it came as no surprise to Mark Mahowald, medical director of the Minnesota Regional Sleep Disorders Center in Minneapolis, who has long contested the dogma that sleep and wakefulness are discrete and distinct states. “There is now overwhelming evidence that the primary states of being are not mutually exclusive,” he says. The blurring of sleep and wakefulness is very clear in status dissociatus, but he believes it can happen to us all. If he is right, we will have to rethink our understanding of what sleep is and what it is for. Maybe wakefulness is not the all-or-nothing phenomenon we thought it was either.

Finally, the piece on out of body experiences covers the work of Swiss researchers who have been studying these states in people with brain disorder, and managing to induce them in volunteers in a number of inventive ways.

Three awesome articles, all worth your time, all open-access. Three cheers New Scientist.

Link to article on sleep states.
Link to article on hypnotic simulations.
Link to article on out-of-body experiences.

In what sounds like a plot from an animated sci-fi film, I’ve just found a remarkable study where Japanese researchers put a Yoga Master in a brain scanner and fired lasers at him because he claimed not to be able to feel pain while meditating.

It turns out that he showed significantly less brain activity in areas typically activated by pain when meditating.

Intracerebral pain processing in a Yoga Master who claims not to feel pain during meditation.

Eur J Pain. 2005 Oct;9(5):581-9.

Kakigi R, Nakata H, Inui K, Hiroe N, Nagata O, Honda M, Tanaka S, Sadato N, Kawakami M.

We recorded magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) following noxious laser stimulation in a Yoga Master who claims not to feel pain when meditating. As for background MEG activity, the power of alpha frequency bands peaking at around 10 Hz was much increased during meditation over occipital, parietal and temporal regions, when compared with the non-meditative state, which might mean the subject was very relaxed, though he did not fall asleep, during meditation.

Primary pain-related cortical activities recorded from primary (SI) and secondary somatosensory cortices (SII) by MEG were very weak or absent during meditation. As for fMRI recording, there were remarkable changes in levels of activity in the thalamus, SII-insula (mainly the insula) and cingulate cortex between meditation and non-meditation. Activities in all three regions were increased during non-meditation, similar to results in normal subjects. In contrast, activities in all three regions were weaker during meditation, and the level was lower than the baseline in the thalamus.

Recent neuroimaging and electrophysiological studies have clarified that the emotional aspect of pain perception mainly involves the insula and cingulate cortex. Though we cannot clearly explain this unusual condition in the Yoga Master, a change of multiple regions relating to pain perception could be responsible, since pain is a complex sensory and emotional experience.

I have an image of scientists shielding their eyes as lasers fail to penetrate the force field of the Yoga Master who serenely hovers a few inches above the ground, although I suspect that’s because I’ve read too many manga comics

Link to PubMed entry for study,

Earlier this year we covered a study on REM sleep behaviour disorder (RBD) where normal sleep paralysis breaks down and sleepers act out their dreams. The Journal of Forensic Science has just published a study on the dark side of the disorder, where affected sleepers experience nightmares and can unknowingly damage themselves or their partners in fits of dream world violence.

The researchers examined all the published cases on violence in REM sleep behaviour disorder with potential for a lethal outcome and found they fall into three groups: choking or headlock attacks, throwing someone or throwing yourself through a window, and diving from the bed.

Some of the descriptions are pretty intense:

A 63-year-old man with RBD and delayed-onset Shy-Drager Syndrome reported “a progressive 10-year history of abnormal behavior during sleep. He would at various times choke, kick, punch, and spit on his wife while he was asleep. In addition, complex behaviors such as getting out of bed and running into walls while asleep were reported by family members. This behavior occurred while the patient was dreaming, usually of being attacked.

A 67-year-old man had a 3-year history of progressive stiffness and slowing of his left side. Five years before the onset of these symptoms, he began having vivid dreams together with violent movements during sleep. Once he dreamed of being trapped in a house on fire, and he almost jumped out of the window, if not for his wife awakening and restraining him.

A 25-year-old woman with multiple sclerosis “presented with a 6-month history of sudden awakenings from fearful, often vivid‚Ķdreams and with terrified screams or violent behavior such as kicking, running to the door or to the window, crying and falling out of bed. If awakened, she always recalled a fighting dream. Once she repetitively banged her head against the floor, inducing a large facial hematoma. On that occasion, she was dreaming that a man was knocking her against the wall.

The idea that someone could be violent during sleep without any awareness was initially treated with suspicion but it has since been confirmed in sleep labs where patient are video-taped and wired up to an EEG to confirm they are in REM sleep.

There have now been numerous legal cases where ‘sleepwalking violence’ has been used as a defence for murders or attempted murders, and at least one case where it led to a successful acquittal.

Link to summary of RBD lethal violence study.

One of the most influential and controversial papers in psychiatry was from a 1976 study published in The Lancet that found that people with schizophrenia had larger fluid filled ventricles in the brain.

Yesterday, I looked up the original paper in London’s Institute of Psychiatry library and was amazed to see that the controversy seems ingrained into the paper copy, which has been ripped, repaired, damaged and defaced.

In the early days of scientific psychiatry, during the 1800s, many famous German psychiatrists expended a great deal of effort examining the post-mortem brains of patients with schizophrenia (also known at that time as dementia praecox) attempting to demonstrate Wilhelm Griesinger’s theory that “all mental illness is disease of the brain.”

Despite numerous studies, they were unable to replicate the success of studies on dementia, which they linked to specific changes in the brain. So for generations, schizophrenia came to be defined as a condition in which the brain was structurally normal.

This fact was often highlighted by the antipsychiatry movement to suggest that ‘mental illness’ was nothing more than a difference in human experience and there was no medical evidence supporting the work of psychiatrists.

But the fact was also cited by many psychiatrists resistant to the relatively new wave of medications that had appeared on the scene. The drugs were claimed to ‘fix’ the brain with the assumption that the discovery of clear evidence for brain differences would just be a matter of time.

Enter Eve Johnstone and her colleagues at Northwick Park Hospital in London, who, in the midst of this politically charged environment, completed a study that compared CAT brain scans of 18 patients with schizophrenia to a group of healthy control participants. Alongside the scans, the researchers also tested the participants’ mental abilities with psychological tests.

The results were striking. They found the size of the ventricles, the fluid filled spaces in the brain, was, on average, larger in patients with schizophrenia and that it was correlated with the degree of difficulty with tests of memory, concentration and problem solving.

This caused enormous interest and controversy at the time. The paper copy from London’s Institute of Psychiatry library clearly reflects this, as it has been read so many times (and possibly ripped out) that it is virtually in tatters and has been reattached with sticky tape in an otherwise pristine copy of the journal.

There are a few annotations on the page, including the word “Rubbish” written in the margin!

Although seminal, the study has been rightly criticised and one of the major difficulties with these sorts of studies is that because patients are normally taking antipsychotic medication, it’s hard to distinguish where the effect is linked to schizophrenia or the treatment.

While some medication is thought to also thought to affect brain structure, a study on patients that have never taken medication seem to suggest some differences in ventricle size, on average, are still apparent.

The ‘on average’ bit is important though, as these differences are not present in everyone with the diagnosis. They’re just an average difference when you compare a group of people with and without schizophrenia. Furthermore, we’re still not quite sure of its significance.

So the topic is still as controversial as when Johnstone’s study first appeared in 1976, although the argument has shifted from whether differences in the structure of the brain are associated with schizophrenia, to whether they are telling us anything useful.

Link to scan of article from Institute of Psychiatry library.
Link to PubMed entry for same.