Category: Inside the Brain

Neuroscientist Larry Cahill has written an in-depth review article for Nature Reviews Neuroscience arguing that understanding the difference between men and women is essential if we are to fully comprehend brain function and behaviour.

Traditionally, research in this area focused largely on sex behaviour, and it has only been during the last decade when the sex differences have been found in other areas.

Cahill notes that this includes “emotion, memory, vision, hearing, processing faces, pain perception, navigation, neurotransmitter levels, stress hormone action on the brain and disease states. Even otoacoustic emissions (audible ‘clicks’ made by the inner ear) differ reliably between the sexes, being both louder and more frequent in female than male adults, children and infants”.

The review examines the increasing amount of research in this area, and dismisses some myths regarding sex differences, including the myth that sex differences are small and insigificant, and that they can largely be explained by the action of sex hormones (such as oestrogen or testosterone) on the brain.

The article is available online as an open-access paper.

Link to Cahill’s article in Nature Reviews Neuroscience.

Controversial findings were recently published in the journal Neurorehabilitation suggesting that the insomnia drug zolpidem roused three severely brain-injured patients from the coma-like persistent vegetative state (PVS).

Zolpidem is better known by its trade name Ambien, and has also been in the news recently for causing unusual sleep behaviour such as sleep-driving.

The study published by Drs Ralf Clauss and Wally Nel reported on three patients diagnosed as being in PVS. All three were temporarily but reliably roused after being given the drug each morning over a period of 3 to 6 years.

It has been suggested, however, that the patients may not have genuinely been in PVS, as this state is thought to be misdiagnosed in up to 40% of cases.

Even if these patients were misdiagnosed, the results would still be interesting for those hoping to find an effective treatment for people who have chronic problems with arousal after brain-injury.

Furthermore, the fact that the treatment was consistent over such a long period is promising. Nevertheless, the drug will need to be tested in comprehensive clinical trials to show that the treatment is widely beneficial and the improvement in these patients was not due to person-specific factors.

Link to abstract of study.
Link to write-up from New Scientist.

Brain Ethics have picked up on a new development in fMRI brain scanning technology that has the potential to detect fast changes in brain activity.

Research just published by neuroscientist Denis Le Bihan and his team has found that changes in brain activation can be detected by measuring water diffusion through neurons.

This type of water diffusion is thought to reflect the activity of the cells, but crucially, it seems it provides a more direct and quicker measure of brain activity than conventional methods.

The majority of fMRI studies use a measure of how oxygen-rich certain areas of the brain are, as it is well known that more active areas take more oxygen from the blood.

One disadvantage, is that this Brain Oxygen Level Dependent (BOLD) measure is relatively slow. It only seems to kick in 1-2 seconds after a brain area has been active and peaks up to 5 seconds later.

The new method from Le Bihan’s team has the potential to improve this process but there are still many unanswered questions, including exactly how the measure of water diffusion relates to the known activities of single neurons or synapses.

Link to ‘An fMRI revolution?’ from Brain Ethics.
Link to abstract of Le Bihan and colleagues’ study.

Omni Brain managed to find a wonderful Dutch website where the neurochemistry of common street drugs is illustrated as step-by-step animations.

If you ever wondered exactly how ecstasy, cannabis, speed, cocaine, heroine, alcohol or nicotine have their effect in the brain, now’s your chance to find out.

The animations give the detailed effects of the drugs on the neurotransmitter systems with an explanation of each of the main effects of the compounds.

Link to Drugs and the Brain animation site (via Omni Brain).

BBC Radio 4 science programme Frontiers examines the psychology and neuroscience of time perception and considers how the sense of time can be warped when we’re put under stress.

In one part, the programme talks to psychologist David Eagleman who’s been running experiments with people doing ‘SCAD diving‘ – an activity where you jump free-fall off a 50 metre crane into a waiting net below.

He asks participants to try and judge time during the jump to see whether the stress of the situation genuinely affects people’s time perception – in an attempt to understand if things really go ‘in slow motion’ during emergency situations.

When a person’s life is in danger, a phenomenon known as ‘time-dilation’ can occur. This is when, during a car crash for example, time seems to slow down or become frozen.

In these cases the body’s internal clock speeds up when facing a potential catastrophe, so that it can take in more information more quickly and function more effectively in an emergency.

This is also a phenomenon actively sought by elite sportspeople, when they get ‘in the zone’.

Some of the chemicals in the brain, such as dopamine, can affect our perception of time. Deficiencies in these chemicals can lead to brain disorders.

In today’s technological age, the body’s natural clocks are being hijacked by timetables, schedules and diaries. By paying more attention to our watches, rather than our internal clocks, could we be losing touch with time as it should be perceived?

Link to Frontiers special on time perception.
realaudio of programme.

Neurosurgeon and author Dr Katrina Firlik has kindly agreed to answer a few questions about her interest in brain surgery and neuroscience.

She also tells me that her new book (featured previously on Mind Hacks) has been released in the UK under the name Brain Matters (ISBN 0297848070).

Apparently, she will be in the UK to talk about her work in the near future, so we’ll post details as soon as we know them.

Anyway, on to the interview…

Continue reading “Five minutes with neurosurgeon Katrina Firlik”

Neurofuture has collected a range of recent posts that have been inspired by recent research on the ‘neurobiological basis of dread’, although a particularly clear description of the study posted to Brain Ethics is, perhaps, a good one that’s missing.

The research was probably best summarised in the mainstream media in an article from Science.

The New York Times had slightly different angle on the story and asked the researchers about how you would go about avoiding feelings of dread.

The first study ever to look at where sensations of dread arise in the brain finds that contrary to what is widely believed, dread does not involve fear and anxiety in the moment of an unpleasant event. Instead, it derives from the attention that people devote beforehand to what they think will be extremely unpleasant.

So the solution to dread, the researchers say, is self-distraction.

Link to abstract of original scientific paper.

Katrina Firlik is a neurosurgeon. She’s one of the few female neurosurgeons in a largely male dominated profession and has written a book about her work and experiences called Another Day in the Frontal Lobe.

She’s recently been featured on numerous radio programmes and newspaper interviews (listed here), the best of which is probably an in-depth discussion about her work on an NPR radio show entitled A Surgeon’s-Eye View of the Brain.

A short excerpt of her book is available online:

The brain is soft. Some of my colleagues compare it to toothpaste, but that’s not quite right. It doesn’t spread like toothpaste. It doesn’t adhere to your fingers the way toothpaste does. Tofu — the soft variety, if you know tofu — may be a more accurate comparison. If you cut out a sizable cube of brain it retains its shape, more or less, although not quite as well as tofu. Damaged or swollen brain, on the other hand, is softer. Under pressure, it will readily express itself out of a hole in the skull made by a high-speed surgical drill. Perhaps the toothpaste analogy is more appropriate under these circumstances.

The issue of brain texture is on my mind all the time. Why? I am a neurosurgeon. The brain is my business. Although I acknowledge that the human brain is a refined, complex, and mysterious system, I often need to regard it as a soft object inhabiting the bony confines of a hard skull. Many of the brains I encounter have been pushed around by tumors, blood clots, infections, or strokes that have swollen out of control. Some have been invaded by bullets, nails, or even maggots. I see brains at their most vulnerable. However, whereas other brain specialists, like neurologists and psychiatrists, examine brain images and pontificate from outside of the cranium, neurosurgeons boast the additional manual relationship with our most complex of organs. We are part scientist, part mechanic.

She’s also an obvious neuroscience geek and has an online gallery of neuroanatomy drawings and a Cafepress store where you can buy t-shirts with them on!

Link to interview and discussion on NPR radio.
Link to Katrina Firlik’s website with book details.

An old suggestion that crossing the visual and auditory pathways to the brain would lead to light being experienced as sound, and vice versa, has been tested and found to be false.

Nicholas Swindale, in Current Biology, 2000

Okay, so this isn’t new news, but it was new to me and too good a story not to share.

If, from birth, the information from the eyes is routed to the auditory cortex then the brain learns to see like normal – at least in ferrets, with whom they’ve done these experiments. The cortex has the potential to cope with whatever information it is provided with during development. So, it seems, the regional specialisations of the brain aren’t genetically predetermined. But a question remains: if your auditory cortex is processing visual stimuli, how are they actually experienced? The brain might be processing the information well enough to guide behaviour, but how do the stimuli actually feel? Are they experienced as visions or as sounds? Or, as Swindale puts it:

are the types of sensory processing that ultimately give rise to qualia innately determined properties of different cortical areas, or are they the secondary outcome of a general purpose learning algorithm applied to sensory inputs which have a different information content?

And, crucially, is there any way of working this out in a ferret? Is there a way of telling what a ferret’s experience is really like? Well, there is, and it involves rewiring just half of the brain – so that visual inputs to one side go to the ‘auditory cortex’ and visual inputs from the other go to the visual cortex as normal. Now if you train the animal to go left to visual inputs on the intact side and right to sounds, which way will it go to a visual input presented to the rewired side? If it experiences the visual input as most like a sound it will go right, but if it experiences it as most like a light it will go left. The animals go left – so visual stimuli are experienced as visual whereever in the brain they are initially processed.

Swindale’s review
The original research von Melchner L, Pallas SL, Sur M: Visual behaviour mediated by retinal projections directed to the auditory pathway. Nature 2000, 404:871-876.

The cover story on today’s New Scientist is about recent efforts to determine what people are thinking by viewing their brain scans.

Although you may think this is what neuroscientists already do, in most brain-scanning experiments the researchers will know exactly what the participants are experiencing in the scanner, and they just link the measured brain activity to the known task.

Recently, researchers have been able to work out what the participants are viewing by only looking at their brain scans.

Although these experiments are quite simple so far – the researchers typically know that the participant is viewing one of several simple options and just have to work out which – the idea that mental states can be ‘read’ is causing some excitement. Not least because this has been the subject of many science-fiction novels and films.

The accuracy of these experiments is typically much better than chance, although it is far from perfect and so far has largely relied on very simple tasks (viewing lines and the like):

In published results, Tong and Kamitani were able to predict correctly 56 per cent of the time which of eight orientations of lines people were seeing, compared with 12.5 per cent for chance. When subjects were shown a grid of criss-crossing lines, the researchers predicted correctly 80 per cent of the time which lines were being attended to (Nature Neuroscience, vol 8, p679, pdf).

Unsurprisingly, this has sparked some neuroethical concerns. For example, the technology might advance to the stage where it could be used to narrow down what people were thinking regardless of whether they consented (e.g. in interrogations).

The article isn’t freely available online, but your local library or newsagent should have a copy.

Link to New Scientist table of contents.
pdf of Kamitani and Tong paper on ‘decoding the subjective contents of the brain’.

Wired has a short piece on researchers from Carleton University who are attempting to use EEG signals in place of a password – so you can think ‘pass thoughts’ to get to your data.

“It is known there are differences between people’s brains and their signals,” says Carleton researcher Julie Thorpe, who’s working on the project with Anil Somayaji and Adrian Chan. “Can we observe a user-controllable signal encoding hundreds or thousands of bits of information in a repeatable fashion? That’s the real question. We think it may be possible.”

The system has the potential to become a new kind of biometric security tool that — in contrast to fingerprint readers, iris scanners or facial recognition — would allow users to change their pass codes periodically.

Maybe this will lead to a new generation of hackers who train themselves to simulate others mental states in an attempt to forge ‘pass thoughts’?

Link to article ‘Your Thoughts Are Your Password’.

The Society for Neuroscience publishes monthly Brain Briefings that explain how basic neuroscience discoveries lead to clinical applications.

The newsletters cover recent advances in neuroscience research and are intended for a lay audience so are jargon free and easily digestible.

The webpage versions (rather than the pdf files) are referenced so you can also follow up any of the briefings by getting deep into the science if you get inspired.

Link to SfN Brain Briefings.
Link to Society for Neuroscience.

This month’s brilliant Out of Mind column in Prospect magazine, written by psychiatrist Robert Drummond and Alexanader Linklater, deputy editor of the mag, is about a cambonian woman with phantom paralysis.

The woman’s husband died recently following a massive stroke. They’d been married 42 years. An earlier stroke had left him with a weak arm and leg. Now his widow is complaining of similar symptoms – a completely limp arm, and a weak leg, but crucially, scans have revealed no physical explanation for her paralysis.

“The young psychiatrist asks if Kim Sieng feels depressed. She says she doesn’t. He asks if she wants to talk more about her husband. Again she doesn’t. Suddenly, he is conscious of a poignancy that Kim Sieng does not herself express. He can’t resist the impression that she has somehow embodied her grief, telling him about it with her body”.

The article describes how the psychiatrist was finding himself in the murky world of ‘hysterical paralysis’, part of Charcot’s 19-th century notion of a dynamic neural lesion.

Here’s how, at a public lecture at the Salpetriere, Charcot describes hysterical paralysis in a male patient, taken from Sebastian Faulks’ outstanding novel Human Traces:

“This is an example of what an English colleague, Mr. Reynolds, referred to as ‘paralysis by idea’ – not imagined paralysis, for this man is as physically afflicted as any of my multiple sclerosis patients – no, paralysis by idea. An experience has been held out of conscious thought in such a way that it has been able to exert its influence directly upon the nervous system and thus upon the muscles of the patient. And that, ladies and gentlemen, is the peculiar interest of this condition”.

Link to this month’s Out of Mind column (which unfortunately isn’t free this time).
Link to last month’s column (free access) on different perspectives of alcoholism.
Link to earlier Mind Hacks post on A Beautiful Madness, highlighting an earlier Prospect article by Drummond and Linklater.

BBC News are reporting that Belgian researchers are using a modified version of Duke Nukem 3D in brain imaging studies – unaware that Duke Nukem has been used in brain-scanning experiments since 1998.

The image on the left is from a 1998 paper published in Science by Dr Eleanor Maguire and colleagues. The paper is available as this pdf.

The Maguire study mapped out areas of the brain involved in navigating through space and spatial memory by editing the standard Duke Nukem game to include controlled tasks.

The brain activation can be seen in the hippocampus and caudate nucleus. The location is the LA Meltdown level. Come get some!

A recent study published in PLoS Biology by the same Belgian neuroscientists mentioned by the BBC extended this research by looking at delayed brain activity associated with learning various tasks. This included a spatial navigation task which also used a modified version of the Duke Nukem environment.

After participants had learnt one task, they were asked to wait before completing another. The learning from the first task induced long-term changes in brain activation which could be detected when participants were doing the second unrelated task.

This suggests that learning is an ongoing and evolving brain process, even when you’ve moved on to other things.

Duke Nukem has now featured in a whole raft of brain scanning experiments, often only described as being a ‘virtual environment’.

Link to badly spun BBC News story.
pdf of Maguire and colleagues 1998 paper.
Link to summary of delayed learning paper.
Link to full text of delayed learning paper.

An innovative study just published in the open-access science journal PLoS Biology provides intriguing evidence that the brain dedicates a region to understanding maths by as early as four years-old.

The researchers, led by neuroscientist Jessica Cantlon, used fMRI to brain-scan adults and four year-old children while they watched collections of shapes flash up in front of them.

In most conditions, the number of shapes and the type of the shapes stayed the same, so participants mostly saw pictures of 16 circles.

On rare occasions, the circles were replaced by squares or triangles, or alternatively, the number of shapes doubled to 32. This last condition was crucial, because it represented a change in the number of shapes presented on screen.

Most other things that could have caused a brain response were controlled for, so a change of brain activation here should indicate a neural response linked to detecting a change in number.

In this condition, both adults and four-year olds showed activation in an area called the intraparietal sulcus, part of the parietal lobe.

This area is known to be particularly involved in sophisticated number processing in adults using Arabic numerals (what we would normally think of as ‘maths’), which suggests that this ability may be based on a very early mechanism for dealing with counting and numbers.

Interestingly, children showed this activation largely on the right hand side of the brain, whereas adults showed similar activation on both sides.

Cantlon and her team suggest that this is because basic number ability becomes more complex as we learn to do symbolic mathematical operations during and after school, which the pre-school children in the study were unable to do.

Link to summary of study.
Link to full text of scientific paper.

The publishing of Scientific American Mind seems to have settled down into a bimonthly cycle with a new issue on the shelves and two of the articles freely available online.

The first tackles how successfully computer simulations of the mind represent genuine human thought and to what extent they will have to rely on simulating other human abilities and attributes – like perception and distributed neural networks.

The second online article looks at the neurobiology of alcohol and what this tells us about alcoholism and booze-related brain impairment.

Other articles, only available in the paid-for version, include a piece by Nobel prize winner Eric Kandel on future challenges for neuroscientists, and a feature article on one of neuropsychology’s current hot-topics: mirror neurons.

Link to AI article ‘Electric thoughts?’.
Link to neurobiology of alcohol article ‘Staying sober’.