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Oh, The Pain of Rejection (and Buying A New iPod) January 31, 2007

Posted by Johan in Social Neuroscience.
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A paper by Eisenberg, Lieberman and Williams kept popping up a few years ago, and the other day a more recent article cropped up, which brought back previous annoyances to the point where I had to make a post about it.

Essentially, Eisenberg et al found that the anterior cingulate cortex, which is known to be active when we experience physical pain, was also active when participants in the study were subjected to social rejection, as part of a ball-tossing game. Naturally, these findings are easily translated into nice headlines. There is something appealing about the notion that the site of social pain would be the same as the site of physical pain. It fits our metaphors – “love hurts.”

Along similar lines of research, a recent paper in Neuron by Knutson et al claims that the insula becomes activated when we are confronted with high prices. The same region, buried deep in the Sylvian fissure, is also activated by the anticipation of physical pain. They report a negative correlation between insula activity and purchasing.

Once again, it’s tempting to interpret these results in terms of metaphor – “a stinging loss.” Anyone who has lost half the vacation budget at a Poker table on the first night knows that there is in any case some kind of pain involved.

However, it is not physical pain. Nor does social rejection physically hurt. I could prick you with a needle and then play a ball game where you never get the ball (this would be the best experiment ever), and I can assure you that the two ensuing responses are quite easy to dissociate. Both these articles seem to be interpreted as though they show that social processes are closely related to physical pain, but perhaps what they really show is that regions we thought to be causative in the experience of physical pain are clearly not, as other stimuli can produce activation without the ensuing experience of pain.

Two caveats: the authors of these two studies have been reasonably careful in their interpretations, and should not be held responsible for how their research is then described in secondary sources. Also, I don’t mean to imply that there is no relationship between physical pain and “social pains.” The two papers I’ve mentioned here both seem to show that such a relationship exists. But it is unlikely to be as simple as a “pain center,” that is activated by all kinds of social and physical pains.


Human Scent Tracking January 30, 2007

Posted by Johan in Sensation and Perception.
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There is an article by Porter et al in Nature Neuroscience on human scent tracking. This is not the result of some psychophysicist trying to bring Vision and Audition’s neglected little brother Olfaction into the spotlight… Rather, it appears Porter et al were interested in the mechanisms of scent-trail tracking in mammals, and had found that most other animals become quite uncooperative when you try to block one of their nostrils.

Nevertheless, the paper reveals that humans have some fairly surprising scent-tracking capabilities. Two-thirds of their untrained participants could track a 10-metre scent trail through an open field, with all other senses blocked (for a fun example, those with access to Nature will be able to see a video of a typical trial). In a second experiment, four participants received 9 sessions of practice, and tracking velocity doubled. Contrary to what you might think, given how close together the nostrils are, Porter et al found that performance was impaired when participants were made to track with only one nostril, or using a prism device that ensured both nostrils got the same input. This suggests that the input you get into each nostril is actually distinct enough to provide meaningful information.

Incidentally, this surprising olfactory ability wouldn’t have surprised Richard Feynman, who described a similar trick in his semi-autobiography Surely You’re Joking, Mr Feynman. He would smell the wrists of his friends, and found that following this, he could identify their wrists by scent alone, when tested. For a Theoretical Physicist, he sure loved his experiments.

I think the fundamental problem for human scent tracking is that our noses are too far from the ground. In the Porter et al paper, the participants were basically crawling on the ground, hands and knees. Humans are just so painfully slow at moving in this fashion that you’re unlikely to ever catch up with any animal you might want to track this way.

GlaxoSmithKline is having a bad week… January 29, 2007

Posted by Johan in Psychopharmacology, Rants.
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The headline at BBC is “Drug Company Hid Suicide Link“, which ranks somewhere close to “our CEO’s real last name is Mengele” in the hall of fame of bad news for pharmaceutical companies. In short, the story uncovered by BBC’s Panorama, which aired just minutes ago here in the UK, deals with a rather untidy web of deception and spin instigated by GlaxoSmithKline to promote their antidepressant Seroxat. While the drug was only FDA approved for use in adults, clinical trials showing potentially suicidal effects in teenage users were suppressed, or spun.

The unusual bit is that as part of a large lawsuit against GlaxoSmithKline, a large amount of documents have been made public, which was the basis of the Panorama documentary. Perhaps most disturbing from an academic standpoint, two rather reputable researchers in Psychiatry, Neal Ryan and Martin Keller, were exposed as having essentially rubber-stamped articles they hadn’t written, and then getting them published with themself as lead author. While no one has been under illusions about the shady nature of clinical trials and the incentives involved in coming to the “right” conclusions in that line of research, rarely has something like this been brought out into the open before.

Still, it’s a tricky business, treating depressed teenagers. It’s perhaps a fine line between a drug that causes someone to become suicidal, or merely fails to stop that person from going through with what they would have done anyway. The Panorama documentary occasionally swayed to the side of sad case studies, which makes for good TV, but poor evidence. It’s not exactly a surprise that bereaved mothers will look for a reason, any reason, or that teenagers on antidepressants will sometimes kill themselves.

To me, the most offensive part of the whole affair isn’t the spin by GlaxoSmithKline. They’re a business, that’s to be expexted. What bothers me is that some fairly reputable academics apparently rent out their names rather indiscriminately.

Drugs and Neurotransmitters January 29, 2007

Posted by Johan in Neuroscience, Psychopharmacology.
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Omnibrain has a post linking to a flash demo on the way various drugs affect neurotransmitter function in the brain: Mouse Party.

Yes, it features mice on drugs. Animated mice on drugs. It’s a little hard to believe that this was actually made at a University, but there you go. As someone who grew up in a time when science education equalled 20-year-old reel-to-reels made by Solfilm (anyone who went to primary school in Sweden will know what I’m talking about), this stuff is pretty impressive.

If you like Mouse Party, check out a more technical flash demo of neurotransmitter functioning and drug use.

More on The Forbidden Experiment January 27, 2007

Posted by Johan in Behavioural Genetics, Cognition, Developmental Psychology.
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While looking around for post-grad opportunities, I somehow stumbled across an article by Rebecca Saxe on feral children. It’s a review of a book by Benzaquen, but only in the loosest sense of the word. One very interesting quote on the forbidden experiment:

But here’s the catch: the forbidden experiment may belong to a smaller group of experimental problems that persistently seem meaningful but are not. Intuitively, we expect that while human nature interacts with human society in a typical child’s development, the natural and the social are in principle independent and distinguishable. If this intuition is wrong, the forbidden experiment is incoherent. In fact, the social and the natural may be irretrievably entangled in development. In part this is because a social environment that includes other human beings is inevitably more natural for a human infant than any wholly artificial environment that could be constructed to replace it. Even the unfolding of innately determined human traits relies on a social environment. For example, virtually every human infant is exposed to a language and learns it; an infant who was never exposed to any language could not possibly speak one. Yet it is the children who do learn a language—through social interactions—who illustrate the natural human capacity.

This is incidentally part of Behavioural Genetics 101 – it is impossible to estimate the relative contributions of genes and environment to a trait in a single individual. The heritability statistic (i.e., the proportion of phenotypic variance that is attributable to genotypic variance) only works on a group level.

It’s quite hard to grok this on a conceptual level: if a trait has a heritability of .9 for a given population at a given time, this does not mean that each individual’s performance was 90 % genes and 10 % how momma treated him (in fact, it gets worse when we consider that environmental variance is typically of the nonshared kind). Nor does it mean that for 9 participants, genes ruled, and for 1 participant, the environment did.

So really, the forbidden experiment would have to use a sample of feral children. Feral twin study, anyone?