Category: Inside the Brain

Science News has an article on studies suggesting increasing links in the brain process involved in drug addiction and obesity, also suggesting that some of the treatments for drug abuse may also be of use in overeating.

When Volkow and her colleagues looked at the brains of 10 obese people, the team found a dopamine-receptor deficiency identical to that in drug addicts. Volkow stresses that obesity seems to be a significantly more complex disorder than drug abuse because many unrelated factors, such as glandular problems, lack of exercise, or a genetic predisposition to storing fat, can lead to weight gain. However, the brains of several of the obese volunteers in Volkow’s study seemed to be telling another story: “These people were compulsively driven to eat as if food were their stimulus of choice,” she says.

More information on the neuroscience of obesity is available in an issue of Nature Neuroscience made available online as an open-access publication.

Link to article ‘Food Fix’.
Link to Nature Neuroscience on ‘Feeding regulation and obesity’.

American Family Physician has an article on the curious phenomena of ‘psychogenic nonepileptic seizures’. These can look like tonic-clonic epileptic seizures; that commonly involve falling to the floor, limb shaking and unconsciousness, but are not accompanied by a disturbance in brain activity, and are thought to be related to underlying emotional issues or psychological distress.

Epilepsy is usually diagnosed with the assistance of an EEG assessment, where unusual brain activity is suggestive of the condition. A short burst of disruption (a ‘slow wave’) is show on the left, from my own epilepsy EEG.

Psychogenic nonepileptic seizures can be diagnosed when the person’s behaviour suggests a seizure, but no brain disturbance is detected.

The idea that symptoms can appear, but are produced by an underlying emotional conflict rather than the normal process of organic disorder has a long history, most associated with 19th century French neurologist Jean-Martin Charcot.

The condition was originally labelled ‘hysteria’, although is now given the less pejorative names of conversion disorder or ‘medically unexplained symptoms’.

The condition is often linked to emotional disturbance and a history of physical or sexual abuse and the presence of other psychiatric disorders. It is often considered that they are an unconcious attempt to express distress or resolve internal conflict.

Importantly, however, the symptoms are not ‘faked’, as is sometimes unkindly suggested. The person concerned typically has little or no conscious control over their symptoms or their effect, which suggests the mind and brain has a capacity for impenetrable self-deception in some cases.

Researchers are now attempting to understand how this happens, with books being published on the psychology and neuroscience of conversion disorder. Nevertheless, despite this recent work, the condition is still largely mysterious.

Link to article on ‘Psychogenic nonepileptic seizures’ (via BrainBlog).
Link to review of Conversion Hysteria: Towards a Cognitive Neuropsychological Account.

Reduplicative paramnesia is the delusional belief that a place or location has been duplicated, existing in two or more places simultaneously, or that it has been ‘relocated’ to another site. It is one of the delusional misidentification syndromes and, although rare, is most commonly associated with acquired brain injury, particularly simultaneous damage to the right cerebral hemisphere and to both frontal lobes.

From a Wikipedia article on reduplicative paramnesia I’ve just created. Enjoy (and excuse the typos!).

A recent brain scanning study has been widely reported as suggesting that Alzheimer’s disease is linked to the brain functions of daydreaming. The actual study is both complex and interesting, although not as clear cut as the headlines make out.

Th research project, led by neuroscientist Randy Buckner, conducted brain scans on 10 people with Alzheimer’s disease and 8 older people without, and also used data from previous studies on young people.

The newly conducted scans looked at how amyloid plaques, damaging accumulations of proteins linked to Alzheimer’s disease, were distributed across the brain. Further scans looked for other types of structural changes in the brain, such as shrinkage.

This distribution was matched with activity from the scans of young people. In contrast to the structural scans, these functional scans looked at how active the brain was.

Normally, functional scans involve participants being asked to do a particular task. In Buckner’s study, however, the activity was from participants who were just ‘resting’ and were not asked to do any specific mental activity – something the researchers called ‘default activity’.

The researchers noted that ‘default activity’ showed a similar pattern in the brain to the distribution of amyloid plaques in Alzheimer’s disease (shown in the image on the right), and have suggested there might be a link.

There are several unanswered questions though, which the researchers themselves acknowledge.

One is simply that ‘resting’ or ‘default’ brain activity is a mystery, no one is quite sure what the brain is doing in this state. ‘Daydreaming’ is just an everyday term that is used, because we assume that’s what we do when we’re not doing much.

In reality, the brain areas highlighted by the study are involved in a range of diverse of contrasting mental activities.

A further difficulty is that the correlation between ‘default activity’ and amyloid plaque distribution was found between two sets of people. More convincing would be if these distributions were found to correlate in the same people.

With these issues in mind, the final difficulty is with interpreting the results. The researchers suggest that mental activity in younger adults could be related to the later development of Alzheimer’s, but there is no clear understanding of how this happens.

My guess is that ‘daydreaming’ is unlikely to be a significant part of this explanation, although as the scientific paper only mentions it in passing, I suspect the researchers don’t think so either.

Link to press release from Washington University.
Link to Reuters story “Daydreaming activity linked to Alzheimer’s”
Link to summary of scientific paper by Buckner and colleagues.

Waaaay back in the early 90’s, trippy videos were part and parcel of rave culture. Now with the Multimedia Neuroscience Education Project, you can relive the days of shiny rendered graphics and techno soundtracks – with a neurobiology twist!

The site, created by a collaborative team based at Williams College, explains synaptic neurotransmission – the process by which chemical signals are passed between neurons.

Four stages are described in detail: the synthesis and storage of neurotransmitters, neurotransmitter release, the role of postsynaptic receptors and the inactivation of neurotransmitters.

As well as outlining the basics of these four stages, specific examples are given to show how particular drugs use these mechanisms to take effect.

Every description has a realaudio-streamed animation to accompany the text, so you can see the process in action. And each video has a home-brew old skool soundtrack.

The videos explaining the effect of anti-anxiety drugs on GABA transmission and the mechanism of action for antipsychotic medication are two particularly fine examples.

Anyone got any veras ?

Link to the Multimedia Neuroscience Education Project.

Scientist David La Puma recently had brain surgery to remove a meningioma. He describes the experience on his blog, and has uploaded pictures of the operation as a Flickr photo set.

As you might expect from a dedicated and inquisitive scientist, the photo set is fully commented, and in the more ‘anatomical’ of the pictures (this one is great), all the parts of the brain are labelled.

Wishing you a speedy recovery David. Many thanks for a fascinating project.

Photo set 1 and photo set 2 of brain tumour removal surgery.
Link to David La Puma’s blog.

The Guardian reports on psychologist Judith Reisman, who argues that pornography is an ‘erototoxin’ that damages the brain, impairing cognition and rational thought:

“According to Dr Judith Reisman, pornography affects the physical structure of your brain turning you into a porno-zombie. Porn, she says, is an “erototoxin”, producing an addictive “drug cocktail” of testosterone, oxytocin, dopamine and serotonin with a measurable organic effect on the brain.”

In the first instance, she’s right. Pornography does physically affect the brain. In fact, everything we experience physically changes the brain in some way.

What Reisman is trying to do, is portray this physical effect as ‘damage’. Furthermore, she argues the damage could be so severe, that an affected person would not be rational enough to engage in ‘free speech’ (notice the leap?).

Unfortunately, her self-published paper The Psychopharmacology of Pictorial Pornography Restructuring Brain, Mind & Memory & Subverting Freedom of Speech (PDF) is highly selective when reviewing the published neuroscience research.

Many of her arguments are based on one-reference claims, and some only on what she calls “extensive documentation”. One unmentioned implication is the fact that, if sexual arousal from pornography causes ‘brain damage’, then so will real-life sex!

Critics note that Reisman is associated with the Lighted Candle Society, a right-wing Christian organisation aiming to promote ‘moral values’ and fund anti-porn brain scanning studies.

Ironically, her paper is prefaced by a note saying it is restricted to adults over 18, as it contains ‘graphic images from mainstream pornography’.

Link to Guardian piece ‘Sex on the brain’.
PDF of ‘The Psychopharmacology of Pictorial Pornography Restructuring Brain, Mind & Memory & Subverting Freedom of Speech’ by Judith Reisman.
Link to critical piece on Reisman’s work.
Link to story from Desert News on the funding of anti-porn MRI studies.

On Sunday night, the BBC ran the first part of their Secrets of the Sexes series which claimed to rank the show’s participants by ‘brain sex‘, on a scale from 100% male brain to 100% female brain.

The trouble is, there is no objective measure of the sex of the brain, making the whole idea of ‘brain sex’ questionable.

During the show, a number of participants complete various tasks, and their performance allows them to be placed along the scale. The BBC even has an online test allowing you to rate yourself.

The rating of ‘brain sex’ seems to be based on Simon Baron-Cohen’s theory that males and females are likely to differ in skills he calls empathising and systemising.

Empathising is described as the ability to understand and relate to others’ emotions, systemising the tendency to understand things in terms of rules or component parts.

Females tend to score higher on Baron-Cohen’s test of empathising, and males on systemising. So how does this get transformed into the concept of a 100% male or female brain ?

Firstly, it assumes that Baron-Cohen is correct about his theory. This is a big assumption as it is still controversial. Among others, psychologist Elizabeth Spelke has noted several important objections.

Secondly, it involves making an absolute statement (e.g. ‘there is a 100% female brain’) from relative data – e.g. ‘females have a tendency to score higher on the empathising test’.

By using another test, however, alternative differences between males and females can be found. In other words, the rating of how ‘male’ or ‘female’ a person’s brain is, depends on what test is used – something which seems to rubbish the idea of describing any brain as a particular sex.

Instead of describing someone as having a ‘50% female brain’, it is more accurate to say, “compared to everyone else’s performance, on these tasks you scored mid-way through the range of typical female scores”.

Some might say the BBC are just trying to communicate science in a straightforward way, but consider how misleading this sounds: “You have a 50% female foot”. Oversimplified to the point of confusion.

Link to BBC ‘Secrets of the Sexes’ website.

A review article in this week’s British Medical Journal questions whether antidepressants have any more effect than placebo.

The report, authored by psychiatrist Joanna Moncrieff and psychologist Irving Kirsch, analyzes data used in previous healthcare recommendations, concerning a class of antidepressants called SSRIs, of which Prozac is the most famous.

They argue that the improvements found in previous reviews of the data have either been so small that they are clinically insignificant, or have been due to errors or biases in analysis.

In response, Darrel Reiger from the American Psychiatric Association is quoted as saying the researchers have “written an article that selectively pulls out negative studies and conveniently ignores or mischaracterizes positive studies.”

Link to BMJ article ‘Efficacy of antidepressants in adults’.
Link to story from Yahoo News.
Link to story from WebMd.com

Mind Hacks favourite All in the Mind has an special on wisdom, learning and the development of the brain through the lifespan:

None of us are getting any younger. As our bodies show signs of wear, so do our brains. We get forgetful, are confronted by new ideas and perplexed by new technologies. The world appears to be moving way too fast, as we sink into memories of the good ol’ days. Eminent neurologist and author Elkhonon Goldberg argues we have no excuse. His message – make your brain sweat if you want to enjoy your mental life to its fullest. And his suggestion is that the two hemispheres of our brain age differently as we wise up.

mp3 or realaudio of programme.
Link to programme transcript.
Link to ABC Radio National ‘All in the Mind’ website.

A paper in science journal Cell reports on a technique for carbon dating brain cells, based on the rise in atmospheric radiation from the testing of nuclear weapons during the Cold War.

This testing resulted in a large rise in world-wide levels of environmental radiation, peaking in the mid-1960s. Because this radiation was absorbed via CO₂, the decay of radioactive carbon in the DNA of neurons can be used to date when these cells were ‘born’.

The study, led by neuroscientist Kirsty L. Spalding, examined the age of neurons in the occipital cortex – an area at the back of the brain important for the visual system.

The researchers found that the cells in this area were as old as the people studied, suggesting that new neurons are not created there.

Until a few years ago, it was thought that humans did not grow new brain cells after birth. It was discovered, however, that neurons regenerate in an area of the brain called the hippocampus, a structure known to be crucial for memory.

It is still unclear whether other areas of the brain regenerate, although this study suggests that, in the occipital lobe at least, neurons are not created anew.

Link to summary of study ‘Retrospective Birth Dating of Cells in Humans’.

The New York Times has an article on people who experience musical hallucinations.

This form of hallucination is interesting, because they are often the only unusual experience a person will have, unlike in psychosis, where hallucinations may be part of a range of anomalous beliefs and experiences.

Patients reported hearing a wide variety of songs, among them “Don’t Cry for Me Argentina” and “Three Blind Mice.” In two-thirds of the cases, the music was religious; six people reporting hearing the hymn “Abide With Me.” Dr. Aziz believes that people tend to hear songs they have heard repeatedly or that are emotionally significant to them.

Neurologist Tim Griffiths has been brain scanning people who experience these hallucinations. He has found that similar areas of the brain are active when a person is hallucinating music, compared to when they are actually listening to music, except for an area called the primary auditory cortex. This is the area of the brain just behind the ears, and is responsible for the initial processing of sounds.

Interestingly, musical hallucinations are often triggered by deafness.

These music-processing regions may be continually looking for signals in the brain that they can interpret, Dr. Griffiths suggested. When no sound is coming from the ears, the brain may still generate occasional, random impulses that the music-processing regions interpret as sound. They then try to match these impulses to memories of music, turning a few notes into a familiar melody.

Link to reg free New York Times article on musical hallucinations (originally via BrainBlog).

UPDATE: There’s a good piece by Carl Zimmer on musical hallucinations here.

Science News has a major article discussing sleep paralysis, the state in which a person can wake, but remains in the paralysed state used to stop movements during dreaming.

Sleep paralysis, sometimes called ‘awareness during sleep paralysis’, to distinguish it from the normal muscle inhibiting function of REM sleep, is now attracting a substantial amount of research.

One paper by researchers Katharine Holden and Chris French (PDF) even suggested that some ‘alien abduction’ experiences may be due, in part, to terrifying sleep paralysis episodes.

Little is known, however, about the exact brain mechanisms which control sleep paralysis (although parts of the brain stem are known to be important) meaning it is has traditionally been difficult to make educated guesses about why paralysis sometimes remains after waking.

Link to Science News article ‘Night of the Crusher’

ABC Radio’s All in the Mind has a special on the neuroscience of orgasm and the use of brain scanning in understanding this complex event.

The programme focuses on work being carried out by a Dutch team, who are now one of a number of research centres who are studying the neuroscience of orgasm and sexual response after it has been neglected for so many years.

Their work has been reported on Mind Hacks before (here and here) but this includes an interview with the lead researchers and commentary from a number of other experts.

mp3 or realaudio of programme audio.
Link to programme transcript.

American TV channel PBS have a lush website to accompany their series ‘The Secret Life of the Brain‘, with many of the video segments online.

They have an episode by episode guide, that examines the development of the brain from birth, through the process of growing up, and into adult years and old age.

Plenty of supplementary material has also been made exclusively for the web, including a Flash driven 3D brain atlas, a guide to current brain scanning technologies and an illustrated history of brain science.

Link to PBS website to accompany ‘The Secret Life of the Brain’.

Wired has a feature article online about research into the neuropsychology of female orgasm and the approach of current lab based studies.

This sort of research is important, because so little is known about the neural basis of sexual function. In particular, the article describes some intriguing findings, that not all nerves involved in genital arousal route through the spinal cord, some may go more directly to the brain.

Unfortunately, the article frames much of the research in terms of drug development for sexual dysfunction, which is so often the case in these sort of pieces. This is perhaps because much of the research may be funded by drug companies.

This shouldn’t mean however, that journalists should uncritically reproduce the assumptions that these sources promote – mainly that sexual dysfunction is defined in terms of someone else’s arbitrary criteria, and is best treated by (usually expensive) pharmaceuticals.

Link to Wired article ‘The Coming Boom’.
Link to an alternative take on sexual neuroscience by sex psychologist Petra Boyton.