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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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Genetics is increasingly making itself felt in the word of neuroscience. Labs all over the world are trying to understand the role played the the genome in the development of the brain, and impressive results are published each month highlighting how genes are expressed in the working brain, influencing learning and behaviour.

The holy grail of this neurogenomic research is, of course, the establishment of a bridge between the genome, the cell biology of neurons and synapses, the neurobiology of cognitive mechanisms, and behaviour – i.e., the four major aspects of the human mind. So far, not many behavioural traits – if any – can be explained fully in terms of the neurobiological mechanisms causing it, the molecular processes involved in said mechanisms, and the genomics underlying it all, but tintalizing results are emerging all the time that hint at what will come. The Hariri experiments Thomas and I have posted about here on the blog constitute one example. The tracing of how gene expression correlates with the learning of songs in song birds is another. [Check out these two sites.]

In lieu of all this, Cognition has decided to put together a special issue reviewing the progress made in genetics relating to the understanding of human cognition. The issue is still in press, but it is already possible to read some of the papers on the journal's webpage. As far as I can tell from the editorial introduction, written by Franck Ramus [available here], the special issue will contain contributions by Simon Fisher, Evan Balaban, Karin Stromswold, Bruce Pennington, James Blair, and Gary Marcus. Of these, Fisher's paper ["Tangled webs: Tracing the connections between genes and cognition"], Balaban's ["Cognitive developmental biology: History, process and fortune's wheel"], and Marcus' ["Cognitive architecture and descent with modification"] are on-line as I write this. I have glanced quickly at the available articles, and from what I can gather they look especially relevant to researchers working within the cognitive neurosciences who are interested in knowing more about how neurogenomics will impact their work.

Naturally, any attempts to root cognition in genetics will stir up controversies, and raise numerous hard questions. I will return to some of these issues in the coming weeks, as I read my way through the paper. Teaser: You are definitly going to hear more about modularity in the coming days!

-Martin

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Monday Paper Survey, June 12

I missed the paper survey last week, but this week we are back in full effect (albeit a day late!).

English,German and Japanese language researchers led by Cathy Price demonstrates in a fMRI study published in Friday's Science that the left caudate nucleus plays an important role in monitoring and controlling which language is used by bilinguals. German-English and Japanese-English bilinguals were tested on a semantic task, and neuronal responses within the left caudate turned out to be sensitive to changes in the language used or the meaning of the words read by the subjects. Very interesting! Incidentaly, voxel-based morphometry analysis of the affected members of the KE Family (where a point mutation on the FOXP2 gene has led to aphasia) showed abnormalities in the caudate nucleus. So, perhaps the time has come for a more concerted investigation into the role played by the caudate in language production and comprehension. [Link to paper.]

Oxford University Press is starting a new journal this summer called Social Cognitive and Affective Neuroscience. Mattew Lieberman is the editor. If you have an institutional access to OUP's journals, you can find a number of paper in press here. Ray Dolan, Hugo Critchley and their group at FIL in London report an intersting experiment targeting the neuronal mechanisms engaged in the processing of sadness. From the paper's abstract: "We investigated whether observed pupil size modulates our perception of other’s emotional expressions and examined the central mechanisms modulated by incidental perception of pupil size in emotional facial expressions. We show that diminishing pupil size enhances ratings of emotional intensity and valence for sad, but not happy, angry or neutral facial expressions. This effect was associated with modulation of neural activity within cortical and subcortical regions implicated in social cognition. In an identical context, we show that the observed pupil size was mirrored by the observers’ own pupil size. This empathetic contagion engaged the brainstem papillary control nuclei (Edinger–Westphal) in proportion to individual subject’s sensitivity to this effect. These findings provide evidence that perception–action mechanisms extend to non-volitional operations of the autonomic nervous system." [Link to paper.] Another fascinating study by Marco Iacobini's group demonstrate that repetitive TMS stimulation of the right parietal cortex induces a "virtual lesion" that disrupts the ability to discriminate between your ow face and that of others. Wow! [Link to paper.]

 

The hyperscanning guys from Baylor College of Medicine in Houston and CalTech have a new paper out concerning the neurobiology of social exchange (Science, May 19, 2006). From the abstract: "During a social exchange with a partner, one fundamental variable that must be computed correctly is who gets credit for a shared outcome; this assignment is crucial for deciding on an optimal level of cooperation that avoids simple exploitation. We carried out an iterated, two-person economic exchange and made simultaneous hemodynamic measurements from each player’s brain. These joint measurements revealed agent-specific responses in the social domain (‘‘me’’ and ‘‘not me’’) arranged in a systematic spatial pattern along the cingulate cortex. This systematic response pattern did not depend on metrical aspects of the exchange, and it disappeared completely in the absence of a responding partner." [Link to paper.] Now, just what is the cingulum doing!

-Martin

 

 

 

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_blogmondaymorning.jpgUh, two paper reviews so close? Good thing there's an abundance of interesting stuff out there. Come to think of it, we could actually run paper reviews every day! Though it would take a lot of time gathering all items, it would certainly be possible. This highlights one of the shortcomings of this (or any) kind of communication: we can only tap into a minor part of all of what's going on. Show the tip of the iceberg, so to speak. Oh well, here goes:

The journal Biological Psychology runs a special issue this month on animal vs. human cognition. Articles include comparisons of hippocampal function, fear conditioning, and the influence of maternal programming on gene expression (!).

In Cognitive Neuropsychology Iftah Biran and colleagues propose a model for understanding alien hand syndrome, in which brain-damaged patients experience their limb performing seemingly purposeful acts without their intention. They suggest a three-factor model: 1) a disinhibited and reactive limb; 2) the limb is under less volitional control; and 3) the person has a relatively intact self-monitoring system. I think that one more level should be added, in between 2 and 3; i.e. 2½) the limb performs automatisms and other unconsciously controlled behaviours.

My story about the new way to use diffusion MRI to measure brain activation really spurred some activity web-wise. We got the number of visitors reaching an all-high with this post. Just a few links here, here, here and here just to mention a few. While at it, we should not forget another promising (and well known) fMRI method, perfusion fMRI (good page here). While this method still needs to be improved, e.g. in terms of signal intensity, it has the advantage over other methods such as BOLD, and now diffusion, fMRI in that it suffers from less susceptibility artefacts. This is a real advantage if you're studying areas close to air filled areas such as the nasal cavities. Areas such as the orbitofrontal cortex and medial temporal lobe (e.g. amygdala, hippocampus, perirhinal and entorhinal cortex, anterior fusiform gyrus and parahippocampal gyrus) are suffering from distortions during BOLD fMRI paradigms, and will do so using diffusion fMRI, too.

The obvious next step would be to compare all three methods, BOLD, diffusion and perfusion MRI, to get an estimate of the best sequences for different tasks. In addition, it could shed light on the workings of the brain, running all three paradigms on a specific cognitive task. By comparing to BOLD and perfusion fMRI we could learn more about the mechanisms behind diffusion MRI. Hm, maybe my next project?

 

I thought Martin was going to blog about this story (if he did, sorry for the duplicate): Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology has sequenced the first nuclear DNA from a Neanderthal! A story in Nature covers it nicely. Should this project be successful, we should have plenty of studies comparing human and Neanderthal genes. As such, they are bound to have an impact on the way we understand our own species.

-Thomas 

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Yes, yes, it's all very embarassing, but I never got around to doing my Monday paper Survey. Sorry, folks. I've been busy getting people to commit to a book I'm editing, and I've been preparing a talk for this event. (If it so happens that you will be participating as well, please come by the Friday "aesthetics" session and say hi!) So, there…Luckily, Thomas has been posting some very nice stuff, giving us the greatest ever number of visitors this Thursday. He also wrote about the very intereting Science study indicating that bonobos and orangutangs may be able to think ahead. In the spirit of this post I thought I would do a themed Saturday Paper Survey to make up for my wrongs, focusing on work on mental time travel (MTT) – i.e., the ability to recall past events and plan ahead.

The major discussion point among researchers on MTT has been whether or not other animals than humans posses it. The best entry point to this discussion is Nicola Clayton et al.'s review paper in Nature Reviews Neuroscience that argues that food-caching birds do have some kind of MTT ability [link to paper here], and a paper in Trends in Cognitive Science by Thomas Suddendorf and Janie Busby that dismisses Clayton's arguments [link to paper]. A short debate between Clayton and colleagues and Suddendorf and Busby ensued [Clayton's letter; and Suddendorf and Busby's reply].

So what does the data say? Volume 36, issue 2 of the journal Learning and Memory is a great special issue on "cognitive time travel in people and animals". Clayton and Suddendorf both have contributed illuminating papers. There are a papers on rats, birds, and great apes, as well as some interesting papers on MTT mechanisms in humans. [Link to whole issue.]

Apart form the fascinating discussion of whether or not other animals share a MTT ability with us, much interest is naturally focused on what cognitive mechanisms actually underlie MTT. A recent study by Lesley Fellows and Martha Farah in Neuropsychologia suggests a dissociation of temporal discounting – a hotspot of current neuroeconomics research – and future time perspective. From the abstract: "The present study contrasted the effects of dorsolateral and ventromedial frontal lobe damage on two distinct aspects of future thinking in humans. Temporal discounting, the subjective devaluation of reward as a function of delay, is not affected by frontal lobe injury. In contrast, a normal future time perspective (a measure of the lenght of an individual's self-defined future) depends on the ventromedial, but not dorsolateral, frontal lobes." [Link to paper.]

-Martin

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You may have noticed that there's a new box to click in the heading above. It will take you to a reading list we have compiled, covering most of what have been written about neuroethics in the academic literature. The list includes papers and books on both the neuroscience of ethics and the ethics of neuroscience. For now, it is just an alphabethical list Thomas and I have written up for our own purposes, but in the future we may well categorize it. We also plan to up-date it continously, so if you spot any lacunae, please mail us suggestions for the list.

-Martin

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We have previously had alerts about how genes affect the workings of the brain, i.e imaging genetics. But could it not also be so that genes affect the size and shape of brain structures? Of course! In a study by Bueller et al. in Biological Psychiatry, it is demonstrated that the BDNF Val Met Allele is associated with reduced hippocampal volume. This, of course, in healthy subjects. Hey, I wanted to do that study!

Does your personality affect how you experience meaning in life? According to a study by Schnell & Becker, it does. In the journal Personality and Individual Differences, they claim that 52% of variance in people's experience of meaningfulness with their life could be explained by their personality. As they conclude "The results suggest that individuals have a predisposition for particular sources of meaning, dependent on their personality. Persons with the capability of self-transcendence as well as extraverted individuals are prone to experience their lives as meaningful. Furthermore, some sources of meaning show positive correlations with Neuroticism—a finding that is cautiously interpreted, but will need further clarification."

Ageing is known to affect a lot of congitive — and neural — functions. Among the latest articles, we find that the atrophy rates for medial temporal lobe structures such as the entorhinal cortex and hippocampus have individual trajectories (see here). In addition, trophy rates of hippocampus, but not that of ERC increased with presence of lacunes, in addition to age.

Another ageing article demonstrates that the excitability of motor regions in older subjects is lower than in young subjects, consistent with the idea that there is an impaired efficiency of some intracortical circuits in old age.

Attention changes in ageing. But do different kinds of attention change individually? It seems so, according to a study by Fernandez-Duque and Black. Their findings provide evidence of different life span developmental and clinical trajectories for each attentional network.

Near-death experiences have been known through centuries, and in most cases people believe that the vivid experiences of this kind counts as one evidence for an afterlife. In Nature a news article questions whether these experiences are really just dreams. Accoding to this article "People who have had near-death experiences are more likely to mix up dreams and reality than those who have not".

-Thomas

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