Month: May 2010

The ‘sound’ of the silent howl

Photo by Flickr user Tambako the Jaguar. Click for sourceNature Neuroscience has an intriguing fMRI brain scanning study where the researchers could work out what sort of silent video clip the volunteers were watching by observing activity in the part of their brains specialised for perceiving sound.

Although silent, the video clips were all chosen to ‘imply’ sound by depicting things such as a howling dog, a piano key being struck or coins being dropped into a drinking glass. This reliably caused activity in the auditory cortex as the brain ‘simulated’ likely sounds.

The researchers used an analysis technique called ‘multivariate pattern analysis’ that can pick out brain activity patterns associated with different types of experience.

In this study, the analysis was set up to work as a ‘classifier’ where the research team entered both the brain scanning data and what video clips the participants were viewing for part of the experiment, and the ‘classifier’ then tried to guess which types of picture were being viewed for the rest of the experiment just by using the brain scan patterns it had learnt earlier.

After being trained on a sample of the data, the ‘classifier’ could identify which type of silent clip (animal, musical instrument or object) the person was watching by analysing the pattern of activity in the auditory part of the brain.

This is a lovely demonstration of how the brain ‘simulates’ the type of neural activity that would normally be triggered by other senses to help flesh out what it is experiencing.

Perhaps the earliest demonstration of this was from several studies that reported activity in parts of the brain specialised for visual perception that was triggered when you try and picture objects in your imagination.

These visualisation studies are an example of where you are consciously trying to ‘simulate’ another sense through active imagination but, as this new study shows, this sensory ‘filling’ in by the brain also seems to happen automatically.

Studies on ‘implicit motion’ provide another demonstration of this. For example, being shown a still picture that implies movement (such as a ball being dropped) will cause activity in V5, an area specialised for motion perception.

Link to Nature Neuroscience study (seems to be open access).
Link to PubMed entry for same.

Every underdog has its day

Slate has an excellent article on why we have a tendency to root for the underdog. It’s a fascinating area because it involves the combination of our perception of fairness, our positive emotional reaction to winners and our biases about what sort of characteristics we think underdogs might have – all of which could be pulling us in different directions.

The article is packed full of relevant studies, but the idea that we consistently over-estimate the success of underdogs particularly caught my eye:

Researchers have found evidence for exactly this phenomenon‚Äîcalled the “favorite-long-shot bias”‚Äîat the horse track. One recent study [pdf] that compiled stats from some 6 million American horse races showed a steep drop-off in the return on winning bets, as the odds against those bets increased. In other words, bettors were throwing money at the underdogs and underbidding on the favorites. That’s not because we get some special pleasure from playing the ponies at 100-to-1, the authors argue. It’s because we tend to overestimate the long shots’ chances.

Link to Slate on ‘The Underdog Effect’ (via The Frontal Cortex).

Full disclosure: I’m an occasional writer for Slate and I consistently over-rate the chances of long-shots.

The civil rights psychosis

The latest All in the Mind from ABC Radio National has a fascinating discussion about how the definition of schizophrenia shifted throughout the 20th century in the USA as it morphed from being a disease of the withdrawn middle class female to being the affliction of the aggressive black man.

The program is an interview with psychiatrist Jonathan Metzl who discusses his new book The Protest Psychosis: How Schizophrenia Became a Black Disease.

Unfortunately, discussions about mental illness and race can quickly starting going round in circles. As we’ve discussed previously, the fact that an ethnic minority has higher rates of mental illness, does not, in itself, provide strong evidence that the mental health system is racist – as this could easily be a reflection of poverty or immigration, both of which have been shown to have been linked to mental illness independently of the skin colour of the peoples concerned.

However, Metzl’s critique is somewhat more subtle and he suggests that in mid-20th century America there were attempts, implicit or otherwise, to pathologise the civil rights movement by shifting the diagnosis for certain conditions – most notably, schizophrenia.

In fact, in 1968, an article in the Archives of General Psychiatry even proposed what was called ‘protest psychosis’, “a special type of reactive psychosis” that affected “American Negroes” which was caused by “the stress of asserting civil rights in the United States”.

At the time, the excessive and ad hoc use of the diagnosis of schizophrenia in the USA led to the famous ‘US-UK Diagnostic Study‘ where the States was brought in line with the standards and definitions used in Europe.

By the way, if you’re a regular All in the Mind listener don’t miss the extra audio that turns up on the blog. Sadly, you can’t download the extra audio directly because it is embedded in a playing widget, but if you mouseover or ‘View source’ you can see the whole URL for the extra mp3s and download by pasting this into your browser.

Link to AITM on ‘protest psychosis’.

Take cover

The cover of the May edition of the neurology journal Brain is really quite lovely.

Each of the circles is an individual EEG brain map of people with movement problems associated with Fragile X syndrome. The signals are evoked in response to word repetition and each activity map has been drawn from a study published in the same edition.

Don’t be fooled be the fact that the circles make up a brain-like shape as a whole, they don’t represent individual points on a single brain, each of the maps has just been arranged in this way for artistic purposes.

The description rather charmingly says “The maps are rearranged into a familiar shape!” The clue is in the title I presume.

Often when I mention the journal to non-neuroscientists they chuckle as the name seems funny. I’m long past the point where it seems at all abnormal but, presumably, if I saw a plumbing magazine called ‘Pipe’ or a fishing magazine called ‘Rod’ I would find them equally amusing.

Link to cover info for May’s edition of Brain.

Saints of the underworld

National Geographic Magazine has a nuanced, tragic and colourful article about the growing numbers of unofficial saints in Mexico that are called on to protect against death in the increasingly turbulent cities, or have been created as revered patrons of the criminal underworld by gangs and drug traffickers.

“The emotional pressures, the tensions of living in a time of crisis lead people to look for symbolic figures that can help them face danger,” says Jos√© Luis Gonz√°lez, a professor at Mexico’s National School of Anthropology and History who specializes in popular religions. Among the helper figures are Afro-Cuban deities that have recently found their way to new shores and outlaws that have been transformed into miracle workers, like a mythical bandit from northern Mexico called Jes√∫s Malverde. There are even saints from the New Testament repurposed for achieving not salvation but success. In this expanding spiritual universe, the worship of a skeleton dressed in long robes and carrying a scythe‚ÄîLa Santa Muerte‚Äîis possibly the fastest growing and, at first glance at least, the most extravagant of the new cults. “If you look at it from the point of view of a country that over the last ten years has become dangerously familiar with death,” Gonz√°lez says, “you can see that this skeleton is a very concrete and clear symbolic reference to the current situation.”

There is an excellent Wikipedia page on La Santa Muerte if you want more background on the deathly figure.

The NeoGeo article also discusses Jes√∫s Malverde, the ‘narcosaint’ that we mentioned in a previous post, who has a remarkable following on YouTube with numerous digital tributes appearing on the site.

Also, don’t miss National Geographic’s striking photo gallery that accompanies the piece.

Link to National Geographic article ‘Troubled Spirits’ (via 3QD).
Link to National Geographic photo gallery for the article.

K-Space Division

This is an amazing summary of a study just published in the latest edition of Magnetic Resonance in Medicine. I have no idea what it’s about but it helps if you read it in the voice of Dr Spock.

Susceptibility mapping in the human brain using threshold-based k-space division.

Magn Reson Med. 2010 May;63(5):1292-304.

Wharton S, Schäfer A, Bowtell R.

[Captain] A method for calculating quantitative three-dimensional susceptibility maps from field measurements acquired using gradient echo imaging at high field is presented. This method is based on division of the three-dimensional Fourier transforms of high-pass-filtered field maps by a simple function that is the Fourier transform of the convolution kernel linking field and susceptibility, and uses k-space masking to avoid noise enhancement in regions where this function is small. Simulations were used to show that the method can be applied to data acquired from objects that are oriented at one angle or multiple angles with respect to the applied field and that the use of multiple orientations improves the quality of the calculated susceptibility maps. As part of this work, we developed an improved approach for high-pass filtering of field maps, based on using an arrangement of dipoles to model the fields generated by external structures. This approach was tested on simulated field maps from the substantia nigra and red nuclei. Susceptibility mapping was successfully applied to experimental measurements on a structured phantom and then used to make measurements of the susceptibility of the red nuclei and substantia nigra in healthy subjects at 3 and 7 T.

When I grow up, I want to be in k-space division just like my father, so I can avenge his death at the hands of the structured phantom.

Link to abstract on PubMed.

Centre of attraction

Women who have a smaller waist in relation to their hips tend to be perceived as more attractive. Some argue this is an evolutionary tendency, a desire for women who are perceived to be more fertile, while others suggest it is just a product of the media who, from porn to Prada, laud the image of small waisted women.

The New York Times covers a fascinating study which tested these ideas in an innovative way – by seeing whether blind men, who have avoided the body-shape bias of visual media, would also find women with a lower waist-to-hip ratio more attractive.

The study, currently in press for the journal Evolution and Human Behavior, was devised by researcher led by psychologist Johan Karremans who tested the idea by using adjustable mannequins.

The blind stood before them; they were told to touch the women, to focus their hands on the waists and hips. The breasts on both figures were the same, in case the men reached too high. The men extended their arms; they ran their hands over the region. Then they scored the attractiveness of the bodies. Karremans had a hunch, he told me, that their ratings wouldn’t match those of the sighted men he used as controls, half of them blindfolded so that they, too, would be judging by feel. It seemed likely, he said, that visual culture would play an overwhelming part in creating the outlines of lust. And though the blind had almost surely grown up hearing attractiveness described, perhaps even in terms of hourglass shapes, it was improbable, he writes in his forthcoming journal paper, that they had heard descriptions amounting to, “The more hourglass shaped, the more attractive,” which would be necessary to favor the curvier mannequin over the figure that was only somewhat less so.

But, with some statistically insignificant variation, the scores of the blind matched those of the sighted. Both groups preferred the more pronounced sweep from waist to hip.

How this preference comes about is another matter of course, and the scientific article apparently suggests that as body scent is also a guide to attractiveness and is partly genetically determined it’s possible that blind men have come to associate body shape with attractiveness via smell.

The explanation sounds a little speculative to me, but the core finding of the study is fascinating.

The NYT article is also a great brief guide to attractiveness and waist-to-hip ratio argument.

Link to NYT on ‘The Anatomy of Desire’.