jump to navigation

Amygdala-Orbitofrontal interplay in cognitive flexibility November 29, 2007

Posted by Johan in Learning, Neural Networks, Neuroscience.
1 comment so far

This rat doesn’t get sucrose, but is probably happier than Stalnaker et al’s rats

Blogging on Peer-Reviewed Research Today’s title may be the least accessible yet, but bear with me; this is an interesting paper. Stalnaker et al (2007) investigated the neural basis of what they call cognitive flexibility – this is a very fancy term for a rat’s ability to handle a conditioning paradigm known as reversal learning. The method that Stalnaker et al used serves as a good example of the paradigm.

Rats were first trained on an odour discrimination task. Poking at one little door that is laced with odour A produces delivery of a tasty sucrose solution. Poking at another little door that is laced with odour B produces delivery of an unpleasant quinine solution (incidentally, quinine is a component in Vermouth, but we’ll assume that these particular rats like their martinis very dry). The actual door that is associated with each odour is varied, so that the rats have to rely on the odour cues alone to learn how to get their treat. Once the rats have achieved a criterion level of accuracy at this task, the contingency reverses, so that odour B now produces a treat while odour A produces quinine. The model finding is that the rats will be slower to learn the reversal than they were to learn the original task.

Stalnaker et al were interested in investigating the role of orbitofrontal cortex (OFC) and the basolateral amygdala (ABL) in bringing about this reversal. There are two basic ideas on how this might work: the OFC might directly encode the preferred stimulus, or the OFC might play an indirect role where it facilitates changes in downstream areas, such as the ABL. So in other words, downstream areas bring about the actual behaviour, while the OFC plays more of a modulatory role in telling the downstream areas when contingencies change.

To test these notions, Stalnaker et al lesioned the OFC in one group of rats, the ABL in another group, and both the OFC and the ABL in a third group. After this, the rats learned the odour discrimination task. The three groups did not differ significantly at this point. In other words, neither area or the combination of them was necessary to learn the task. Next, the rats went through two serial reversals – odour A switched places with odour B, and then back again. The effect of the brain lesions was measured by the number of trials taken to learn the reversals to the same accuracy level as the initial odour task.

Rats with OFC damage were slower to learn the reversals than the other groups. However, rats with ABL lesions and rats with combined OFC and ABL lesions did not significantly. So in other words, although OFC lesions in isolation cause impairments, this effect is abolished when the ABL is sectioned as well.

Stalnaker et al interpret these findings as support for an indirect role for the OFC in reversal learning. The ABL is stubborn, simply put. Without the modulatory influence of the OFC, the ABL persists in responding as though the contingency had not reversed, which produces slower reversal learning. By removing the ABL as well, this persistent influence is gone and reversal learning can occur normally. It is somewhat counter-intuitive that lesioning more of the brain helps, but there you go.

This is a nice study because it answers one question, but asks a number of new questions. If the rats can carry out reversal learning normally without either the OFC or the ABL, why is this circuit even involved in the paradigm, that is, why should OFC lesions have an effect, if the pathway as a whole is not needed? Also, if the ABL produces such deficient behaviour when the OFC is lesioned, why don’t lesions to the ABL affect behaviour? And most importantly, if behaviour is normal after ABL and OFC lesions, which other area must be lesioned to impair behaviour yet again. And what happens if this area is lesioned in isolation?

Enough questions to make your head spin, but the take-home message for those studying humans is that there is an entire range of complex interactions in the brain that fMRI, with its blurry temporal resolution and lack of experimental manipulation, can only hint at. We know much about functional localisation in the human brain, but the issue of how these areas connect and interact is largely uncharted territory.

Stalnaker, T.A., Franz, T.M., Singh, T., and Schoenbaum, G. (2007). Basolateral Amygdala Lesions Abolish Orbitofrontal-Dependent Reversal Impairments. Neuron, 54, 51-58.

Evidence for shallow voters, or mere exposure? November 15, 2007

Posted by Johan in Applied, Face Perception, Social Psychology.

Picture by Brandt Luke Zorn, Wikimedia Commons

Blogging on Peer-Reviewed ResearchIacoboni has gotten in trouble recently for some bizarre, non-peer reviewed and much publicised studies investigating voters’ neural reactions to the different presidential candidates. Vaughan noted that it is a little surprising that Iacoboni, who has done some fantastic work, would put his name on such weak research. I couldn’t help but be reminded of a post over at Dr Petra Boynton’s blog on the shameless proposals she has received from marketing companies. Essentially, the business model is that you as a researcher either gather some junk data yourself for handsome compensation, or alternatively, you simply sign off on a ready-made article. It is a credibility-for-cash transaction.

Unfortunately, such spin doctor stories might get in the way of real research on voter behaviour. In the latest issue of PNAS, Ballew and Todorov (2007) report that election outcomes can be predicted from fast face judgements in participants who know neither of the candidates. In other words, to some extent voting behaviour is influenced by quick judgments of appearance – maybe the guy with the better hair really does win. Although this study is very interesting, there are a few shortcomings that will be discussed at the end of this post.

Ballew and Todorov gathered pictures of the winner and the runner-up from 89 gubernatorial races. The pairs were shown to participants, who picked the candidate that seemed more competent (other measures were also used, but I’ll spare you the details). In order to avoid familiarity effects, Ballew and Todorov also included a check for whether the participants recognised any of the candidates. Trials in which the participant did recognise a candidate were excluded. The paper contains three experiments, of which I will cover the first two.

In experiment 1, participants were specifically instructed to base their decision on their gut feeling of which candidate would be more competent. The stimuli were presented for 100 ms, 250 ms, or until the participants responded.

Across all conditions, the competence judgements were significantly above chance (50 percent) in predicting the elected candidate. The three conditions did not differ significantly amongst themselves. Looking across all races, the participants’ averaged “vote” achieved an accuracy of 64 percent in predicting the election outcome. This may seem like a trivial increase over chance, but keep in mind that the participants based this decision on only a very brief exposure to an unfamiliar face. The fact that they could predict the winner suggests that voter behaviour is to some extent determined by the same type of fast, automatic evaluations.

In experiment two, Ballew and Todorov sought to investigate whether this effect could be modulated by the instructions that the participants received. Since Ballew and Todorov are advocating the notion that these judgments are automatic and fast, it becomes important to show that participants gain nothing when they have more time to plan their response. Thus, one group was instructed to deliberate carefully over their decision, and were given no time limits for viewing or responding. A response deadline group viewed the stimulus until they responded, which they had to do within 2 seconds. Finally, the 250 ms condition from experiment 1 was replicated for comparison.

In addition to this, Ballew and Todorov restricted the candidate photos to pairs in which the candidates shared the same gender and ethniticity. This was done since results in experiment 1 indicated that predictions were stronger for such pairs.

As in experiment 1, participants in all conditions were significantly more likely to pick a winning candidate. However, when investigating how each group’s “vote” predicted the election outcome, the deliberation group was not significantly above chance, while the two short-exposure non-deliberation groups were above chance, achieving an average accuracy of 70.9 percent between the two. In other words, careful deliberation and slow responding actually hindered performance.

I think these results are nice, since they offer an explanation for why candidates are so well-groomed (particularly the winners), even though no voter would ever admit to basing their choice on the candidate’s appearance. However, I see two issues with this research. First, although Ballew and Todorov asked their participants to rate competence, was this really what the participants were responding to? Given the fast processing that was necessary in the conditions where the participants performed well, it is perhaps unlikely that they were able to incorporate the instructions. Ballow and Todorov compared the ‘gut feeling’ instructions to a condition where participants were asked deliberate, but unfortunately they confounded the ‘instructions’ variable by giving the participants in the deliberation group unlimited time, in addition to different instructions effectively. It would also have been nice to see a control condition where participants indicated which face was more attractive rather than more competent, to show that participants were responding to something more abstract than attractiveness.

The second problem is more fundamental. Ballew and Todorov used participants from the US who viewed US gubernatorial candidates. In other words, it is likely that participants had been exposed to some of the candidates beforehand. We know from a phenomenon called the mere exposure effect that we tend to like things that we know better. It is not unlikely that winning candidates received more media exposure, so the participants may simply have responded to their increased familiarity with the winning candidate.

Ballew and Todorov tried to control for this by removing trials where the participants reported that they recognised the candidate, but this may be insufficient. Research on the mere exposure effect shows that even subliminal exposure to an object can increase self-rated liking for it. So even if the participants didn’t recognise the face, they may still have been exposed to it, and this may have biased their ratings. You might also think that winning candidates may have gained more exposure simply by acting as governor following the election. However, this account can be ruled out by the third experiment, which I haven’t reported here. Essentially, Ballew and Todorov replicated their findings with voters before an election.

To rule out mere exposure effects more conclusively, Ballew and Todorov would have done well to use candidates from local elections in other countries, where any kind of prior exposure would be more unlikely. You can’t help but feel that in using US voters and US guvernatorial candidates, Ballew and Todorov are sacrificing accuracy of measurement for face validity and impact. It is quite powerful to show that US voters respond this way to US candidates – it drives home the point that this is an effect that likely operates outside of the lab too. That being said, I’m not sure if this is a reasonable trade-off to make.

Finally, it’s worth noting that even if Ballew and Todorov’s results really do measure mere exposure (we would need to carry out more research to confirm that), that doesn’t render the findings invalid. It merely means that the mechanism that brings about the behaviour isn’t fast, automatic judgment of facial features, but fast, unconscious biasing based on prior exposure.

Ballew, C.C., and Todorov, A. (2007). Predicting political elections from rapid and unreflective face judgments. Proceedings of the National Academy of Sciences (USA), 104, 17948-17953.

Encephalon #35 arrives November 7, 2007

Posted by Johan in Abnormal Psychology, Links, Neuroscience.
add a comment

The latest issue of Neuroscience blogging carnival Encephalon is now online over at Primate Diaries.

My two picks of the issue would be two stories on Autism: Not Exactly Rocket Science reports on an experiment that is consistent with the ever-controversial idea that autism is linked with a deficient mirroring system. Also, Medopedia explores some possible reasons why people with Asperberger’s, that is, high-functioning Autism, frequently experience sleep disorders.

It’s the socialising, not just the bingo: new take on brain training November 5, 2007

Posted by Johan in Applied, Cognition, Social Psychology.

Blogging on Peer-Reviewed Research

Brain training is everywhere these days. From the Nintendo DS phenomenon Dr Kawashima’s Brain Training to the Neuroscientist-endorsed Mindfit, it is suddenly obvious to everyone that giving your brain a proper workout is as important to warding off dementia as getting your pulse up a few times a week is to avoiding heart disease.

I confess to being skeptical. Will my brain really benefit if I suffer through a mind-numbingly tedious working memory task? I think it depends on what your alternatives are. If your alternative is to sit silent in front of the TV, I suspect you will benefit, but isn’t there some other, less boring activity that might also help your brain?

A paper by Ybarra et al (in press) suggests that the answer to that is yes, and the alternative is socalising. Ybarra et al combined correlational and experimental designs to arrive at this conclusion. First, they used questionnaire data to show a positive relationship between the number of social interactions and cognitive functioning. The relationship held for all age groups (24-96), while controlling for a range of other factors.

This is a nice finding, but since there is no experimental manipulation, it is just as valid to interpret the findings to mean that intelligent people socialise more. So Ybarra et al went a step further, and recruited participants for an experimental study.

Participants were randomly assigned to three groups, where each group spent 10 minutes carrying out their task: the social interaction group discussed a current political issue, while the intellectual group did reading comprehension and mental rotation tasks, along with a crossword puzzle. There was also a passive control group who simply spent 10 minutes watching Seinfeld.

In order to assess how these different tasks affected cognitive functioning, Ybarra et al estimated processing speed via a task where participants made same-different judgements about dots, and a working memory task, where participants were read sentences which they had to answer questions about, all the while keeping a section of the sentence in memory.

The table below gives the results.

While the scores for the social interaction and intellectual groups are similar, the passive control group appears to have fared worse. Indeed, significance testing revealed that on each task, the experimental groups did significantly better than the passive control group, while the social interaction and intellectual groups did not differ from each other.

It is worth noting that the intellectual task is quite similar to the type of tasks that brain training programs consist of. These results indicate that instead of suffering under Dr Kawashima, you might as well get into an argument over politics with a friend (The alternative and equally valid interpretation of the data is that watching Seinfeld rots your brain). Discussing politics might just be more fun in any case – Ybarra et al did ask the participants to rate the tasks, but found no significant difference in how much the participants liked their tasks. Still, I would argue that most people will choose a debate over a working memory task any day.

This study is quite inspiring in that a single 10-minute session of intellectual or social stimulation was enough to bring about significant differences in task performance. Furthermore, it really is a testament to the power of social interaction that the intellectual task group didn’t come out ahead, even though they had basically spent 10 minutes doing very similar tasks to the ones they were assessed with. However, a few caveats should be considered. First of all, although the intellectual task resembles actual brain training, they are not one and the same. I would love to see a direct comparison between something like Mindfit and the social interaction condition used here. Secondly, although I wasn’t entirely serious about the possibility of Seinfeld rotting your brain, the fact that performance was tested immediately following the 10-minute training session is potentially problematic. It may be that carrying out an activity, any activity, simply raises your overall awareness more than watching TV does. It would have been nice to see a re-test the following day. Finally, this test only shows an immediate effect. If social interaction is to be taken seriously as an alternative to brain training, more longitudinal studies are needed, where regular training over a longer time is used.

So to conclude, these results indicate that bingo isn’t only good for granny for this reason:

But also for this reason:

Ok, so this particular bingo game might not be to granny’s taste, but you get the point.

Of course, no one can sell you social interactions, so expect brain training business to continue as usual.

Ybarra, O., Burnstein, E., Winkielman, P., Keller, M.C., Manis, M., Chan, E., and Rodriguez, J. (in press). Mental exercising through simple socializing: Social interaction promotes general cognitive functioning. Personality and Social Psychology Bulletin.

Thanks to Flickr users monkey123, Keees, and aphrodite-in-nyc for fantastic pictures.


Get every new post delivered to your Inbox.