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Archive for November, 2007

sadchild.jpegPhysorg reports about an interesting forthcoming MRI study linking paedophilia to regional changes in white matter. Analysing structural MRI using voxel-based morphometry, paedophiles were found to have significantly smaller white matter volumes in specific regions, as the abstract demonstrates:

The present investigation sought to identify which brain regions distinguish pedophilic from nonpedophilic men, using unbiased, automated analyses of the whole brain. T1-weighted magnetic resonance images (MRIs) were acquired from men who demonstrated illegal or clinically significant sexual behaviors or interests (n = 65) and from men who had histories of nonsexual offenses but no sexual offenses (n = 62). Sexual interest in children was assessed by participants’ admissions of pedophilic interest, histories of committing sexual offenses against children, and psychophysiological responses in the laboratory to erotic stimuli depicting children or adults. Automated parcellation of the MRIs revealed significant negative associations between pedophilia and white matter volumes of the temporal and parietal lobes bilaterally. Voxel-based morphometry corroborated the associations and indicated that the regions of lower white matter volumes followed, and were limited to, two major fiber bundles: the superior fronto-occipital fasciculus and the right arcuate fasciculus. No significant differences were found in grey matter or in cerebrospinal fluid (CSF). Because the superior fronto-occipital and arcuate fasciculi connect the cortical regions that respond to sexual cues, these results suggest (1) that those cortical regions operate as a network for recognizing sexually relevant stimuli and (2) that pedophilia results from a partial disconnection within that network.

Now, a few things strikes me odd in this analysis and interpretation. First of all, why is the comparison group nonsexual offenders? After all, that the crime is of a sexual nature is absolutely central to the present question, and especially that the sexual offender has been interested in children. The obvious choice would be to compare paedophilic sexual offenders to sexual offenders who had adult victims (typically a male offending a woman). Here, the act of sexual offence is similar between the two groups, while the sexual “object” is the vital difference. In the present study, any significant difference could just as well be explained by the nature of the crime as the sexual inclination of the subjects. It’s a classic case of poor control of confounding variables.

Second, I strongly dislike the over-interpretations offere in both the article and the news story. First, the authors find significant differences in the superior fronto-occipital and arcuate fasciculi, and link these regions to studies showing involvement in response to sexual stimuli. Following this, they suggest that paedophilia may occur due to a disconnection in this network. Just based on the reasons given in the previous section, these results may be interpreted just as well as brain alterations in sexual offence in general.

But more than this, if one just skims the literature on these regions (fasciculi), one can see that they have been implemented in language lateralization/function and hallucinations and delusions. So interpreting the differences as relevant to paedophilia is a long shot.

Furthermore, the physorg story suggest that this study:

challenges the commonly held belief that paedophilia is brought on by childhood trauma or abuse. This finding is the strongest evidence yet that paedophilia is instead the result of a problem in brain development.

This is a serious over-interpretation of the results. When understanding white matter (and any brain) changes during development, one should be cautious to claim that the changes observed are the mere cause of “brain development” and not experience-related phenomena. Here, we need to divide between two effects: neurogenetic and psychogenetic effects. Neurogenetic effects are, in this story, changes in the brain that are caused by biological factors. Age-related atrophy is a good example of this. The cause is the accumulation of junk within cells/neurons that eventually hinder cell division and function. Psychogenetic factors, on the other hand, are observed brain changes that are caused by behaviour, in its broadest sense. For example, if you learn to juggle, areas in the motor regions of the brain will alter their size and connectivity to a measurable extent. Likewise, London taxi drivers are known to have larger posterior hippocampi as a result of their prolonged training in navigation.

So in the case of paedophilia, observed changes in the brain cannot be said to support a brain-based (neurogenetic) interpretation, and to challenge psychogenetic causes. Rather, it has been suggested that many paedophiles have been subject to similar maltreatment when young. At the least, just because the brain shows a difference, one cannot conclude anything beyond this about causation.

As neuroscience enters the domain of social sciences, it holds the promise to both enlighten and naturalize these age-old discussions. However, the use of mere reporting and tailored interpretations are far from sufficient, and may even lead us astray in the goal to achieve a better understanding of these, and related, phenomena.

-Thomas

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hooligans.jpgCan we rid ourselves of the meaningless violence and aggression seen in society today? A news story in Nature News this week shows that aggressiveness may be treated with a serotonin-acting ligand. At least in rats, but nevertheless the study holds the promise for human treatment as well. Serotonin levels are known to be associated with aggression. The lower the serotonin level, the more aggression. So what dd the present study find?

The team engendered violent characteristics by introducing feeble intruder rats that were bound to lose battles, each day for two or three weeks. After repeated victories over other rats, the test animals began to behave in a more pathologically violent manner, fighting all-comers more brutally — including weak females and senseless males which presented no threat to them.

Then the researchers looked at levels of the neurotransmitter serotonin in the rats’ brains. Although brain levels of serotonin don’t change in rats as a result of normal, ‘appropriate’ acts of aggression, the team found that these levels did sink in his pathologically aggressive rats.

So this is more or less a replication and strengthening of previous research, only this model seems to have additional advantages. But the big news came when the team tried to manipulate the serotonin levels in the rats. Here, they found that…

(…) they could alter the aggressive behaviour of their rats by manipulating the serotonin system. They gave the rats S-15535, a compound that binds exclusively to a neuron ‘autoreceptor’ that acts to dampen the serotonin system. This autoreceptor is called 5-HT1a. Binding to it seems to bring serotonin levels in the rats back to normal. When even very low doses of S-15535 were used to bind to the receptors, de Boer found that both the serotonin and the violence of the pathologically aggressive rats returned to normal levels.

Better still, the drug did not seem to affect other behaviour, and did not seem to be generally sedative. So the study suggests that (pathological) aggression might be controlled better using a serotonin-acting drug. The study described in the Nature News was headed by Sietse de Boer from the University of Groenigen. There’s also a story about de Boer study from this year’s SfN conference (I couldn’t make it there, duh), and a ScienceDaily article nicely relates this to other studies.

Of course, the ethical questions are unanswered still. Indeed, if we are able to synthesize these drugs, and they work, who should have them? Should they be forced upon a subject? And let’s make it even more edgy: should it be taken by people (men) going to football matches, and could one convict a hooligan to take a pill before attending a game? Is this the cure for domestic violence, bar fights, hooliganism?

-Thomas

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sciencefraud.jpgMartha Farah just alerted me about her recent comment in the Neuroethics & Law blog. Yesterday, NY Times ran a story about neuro-politics. More precisely, they presented a study of how subjects’ brains responded to, e.g., different political words and pictures of US politicians involved in the 2008 presidental election. The article’s first author is Marco Iacoboni from UCLA. Basically, the researchers give subjects different kinds of tasks, report activations in different regions of the brain (that themselves are likely enough to be involved during the tasks). Then, the authors set out to interpret this activity, such as:

When we showed subjects the words “Democrat,” “Republican” and “independent,” they exhibited high levels of activity in the part of the brain called the amygdala, indicating anxiety

Didn’t I just say that the amygdala is involved in positive emotions, too? So what does amygdala activation mean, then? Studies have also shown that mere emotional uncertainty (e.g., a neutral face) may activate the amygdala. So maybe the political words are just more emotionally ambiguous? Let’s take another one from a different part of the article:

With Mr. Giuliani, the reactions are reversed. Men respond strongly to his initial still photos, but this fades after they see his video. Women grow more engaged after watching his video.

OK, where did men respond more strongly? The whole brain? WOW! Let’s continue to a third place in the article:

Our subjects also exhibited a much stronger empathetic response to a minute-long excerpt from a stump speech by Mr. Thompson than they did to an excerpt of a Giuliani speech.

So what was compared? Two speakers, two political opponents, two speeches, or ___ (add your favourite). OK that’s just three examples, but the article is full of such tea-leaf reading. It’s nothing short of magical thinking, astrology or healing. Put differently, the authors look at brain blobs and try to interpret their meanings in terms of previous knowledge. Is that bad? Yes it is, because it does not even attempt toput up testable hypotheses. And why don’t we get to know what is meant by “more active” or “respond more strongly”? What is this activation compared to? What is the contrast, the baseline? Even further, what is the statistical cutoff and how many other regions light up during conditions X, Y or Z? Where are all the tech specs that validate this study?

So is this really our brain on politics? Or is it the Iacobini team’s own ambition to get publicity (and maybe earn some money along the way)? I’d say the latter is the case here. The basic problem is that we don’t have a scientific reference, and only have to take the authors’ word for it. It’s a violation of every sensible way to report findings from a scientific method in the press. IMO, before you can do such a thing, you should at least (!) have a manuscript that is accepted, let alone published. And if you choose to do a test for the media, just “for fun”, then say so! This article pretends to be scientifically correct. It is not.

How this has come through the press is probably the most interesting story. And how it got through the science editors at NY Times is a mystery. Indeed, I hope that more criticism will force NY Times to send out a corrigendum.

-Thomas

NOTE: As I hoped for, this story has spurred a lot of discussion, e.g., here.

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amygdalaoid.jpegThat almond-shaped structure we call amygdala is typically thought of as solely (or mainly) involved in negative affect. However, some studies have suggested that the amygdala is also involved in other processes, such as novelty (of faces). It should come as a big surprise, however, to many researchers that this structure is also involved in positive emotions. It runs counter to many ideas and interpretations of amygdala activation in, e.g., fMRI studies.

Even more so, in a recent paper in TICS, Elisabeth Murray from the NIH put forth three distinct claims regarding amygdala function (and structure):

  1. amygdala plays a role in positive affect, and therefore not exclusively — or even mainly — in negative affect
  2. contrary to an influential model, recent evidence points to a distinction between emotion and reward and contradicts previous conclusions about the role of the amygdala in reward processing
  3. the amygdala is not a single “thing” but a conglomerate of structures playing different roles in emotional and non-emotional processes

The research reviewed is, as always in the case of Murray, well supported and yet controversial. To anyone studying emotions and reward, it’s a must-read. But even to people studying other functions and regions, it’s a principal discussion and a well-needed lesson in the still-present oversimplified neo-phrenology seen in cognitive neuroscience.

So next time you see the amygdala light up during a brain scan, resort from interpreting it as a sign of anxiety or fear.

-Thomas

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sad-dog_resized.jpgIt should come as no surprise to you that after a prolonged hibernation, the BrainEthics team is heading back to the web-surface to present the novelties and oddities of cognitive neuroscience. And let’s start again with some fresh news from Nature, which besides featuring a nice focus section on the Drosophila, also has a nice article on (non-human) animal personality. Max Wolf et al. writes that personality has been shown in a number of other animal species. For pet owners such as myself, this is hardly any surprise (I can read that the cotons we have here are” playful, affectionate, intelligent breed. It loves people and as a result can have separation anxiety”. Indeed! But with the two we have, there are differences that are not only slight, but what I would say differences in temperament, or maybe even personality.

So what is new with the Nature article? Three things:

  1. it is a scientific acknowledgement of animal minds and personality
  2. it holds promise of the operationalization of personality
  3. it provides a model to explain the existence of human personality

As a matter of fact, I can see a whole new research field coming to existence through this very article (although the earliest findings already came in the 60’s). Through the study of animal personality, it may be possible to break down the good ol’ paradigms that have solely focused on humans.

The central theme in the Wolf paper is why personalities did evolve in the first place. The researchers ask the question:

First, why do different personality types stably coexist? Second, why is behaviour not more flexible but correlated across contexts and through time? And third, why are the same types of traits correlated in very different taxa?

Basically, the authors’ model starts by assuming that an individual can either reproduce now, but having acquired low-quality resources, or delay reproduction by one year, having acquired high-quality resources. For example, an individual that becomes sexually mature at a young age will have to balance the benefit of early reproduction against the cost of reproducing at a smaller size. Individuals that postpone reproduction must be able to survive to realize their reproductive expectations, and should therefore be generally risk-averse, whereas the opposite is true for those planning to reproduce early. So stable individual differences in risk-taking behaviours can evolve and be maintained when there is a trade-off between early versus late reproduction.

I won’t go more into details now, except point you to the ongoing discussion in Nature about this article (here and here). It’s certainly also going to get non-biologically personality theorists out of their armchairs, too. I look forward to keep an eye on this debate as it rolls out.

– Thomas

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