Thursday, December 11, 2008

101 Fascinating Brain blogs

OEDB has put together a list of 101 fascinating Brain blogs and it is an excellent list with most of the usual suspects and some new ones too. The descriptions of the blogs are good and informative. The Mouse trap has been featured under Multidisciplinary blogs and I cannot agree more. The focus of this blog has been multi-disciplinary and I am by nature drawn to anything and everything that is remotely tied to brain, no matter what the discipline or the methods.

On a related note, I had thought that the mouse trap being featured in WIKIO Science top 100 was a one-off affair, but it seems that the ranking has only improved this month (the mouse trap is up at #78 this month); so thanks again to all the readers of this blog for continuing to read and link. BTW, I saw a significant drop (about 10%) in the number of RSS feed subscribers after my 26/11 and 'Beyond revenge' post; maybe the subscribers thought that I had decided to leave science blogging for good and thus unsubscribed; political blogging for me may lie in the future, but not for now; for now I intend to continue blogging about brains only. The Mouse Trap blog, at the least, will always remain focussed on psychology and neuroscience only. If  I do decide to blog about political matters I'll maybe start a new blog, just like The Fool's Quest blog which I use for poetry and literature.

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Tuesday, December 09, 2008

Novelty Seeking and Reward Dependence: the dopamine white matter connection.

I had earlier wrote extensively on Cloninger's personality temperaments and proposed that dopamine lies behind the trait Novelty Seeking; while norepiniphrine lies behind Reward Dependence trait. New research , as reported in Nature Neuroscience makes me rethink some of that simplistic schema.

As per Cohen et al, they have found a double dissociation between white matter connectivity between dopamine and sub-cortical and cortical regions and found that these white matter connectivities differentially predict and correlate with traits novelty seeking and reward dependence. Let me quote from the article:

Myriad cognitive, emotional and motor functions of the brain rely on the integrity of the striatum and on interactions between the striatum and other cortical and subcortical networks1, 2, 3. Lesion work in animals supports the idea that fronto-striatal connectivity is crucial for aspects of behavioral adaptation and learning. In these cases, it is clear that anatomy constrains function. Here, we investigated whether anatomical connectivity underlies more global aspects of behavioral and cognitive organization: human personality. We found that the strength of connectivity between two different striatum-related networks predicted individual differences in self-reported personality traits in humans.

Then they go on to show which two networks they studied and found the dissociation in.

In humans, novelty seeking is characterized by impulsivity, exploratory drive and excitability, and has been proposed to be driven by individual differences in dopamine system sensitivity. In rats, both striatal dopamine and hippocampus inputs modulate novelty seeking, linking these structures into a network for novelty detection. The hippocampus may support novelty seeking in part by signaling when sensory input differs from memory-driven expectations (that is, a sensory prediction error), whereas the amygdala may support novelty seeking by modulating hippocampal and striatal activity in novel environments or during emotional memory encoding. Our findings provide additional support for this novelty-loop theory by demonstrating that the hippocampus– and amygdala–ventral striatal pathways are related to stable individual differences in novelty seeking personality.

High reward dependence is characterized by several cognitive, emotional and social facets, including enhanced learning from reward signals, persistence in repeating actions associated with rewards, high sociability and reliance on social approval. These functions recruit the striatum, including dorsal regions. Indeed, the tracts predicting reward dependence were not confined to one particular subregion of the striatum, but were instead observed in striatal areas in which there were strong inputs from these seed regions . This suggests that the white-matter circuits subserving reward dependence are distributed throughout multiple cortico-striatal loops. These loops have been linked to processes ranging from reward learning to cognitive control to action selection.

From the above it is clear that the striatal dopamine system is implicated in both Novelty seeking and Reward dependence. While the implicit, first-line, sub-cortical 'emotional' and unconscious processes sub served by hippocampus and amygdala may be the white tract inputs to the striatum that result in Novelty seeking behavior; the explicit, second-order, cortical, 'cognitive' and conscious processes sub served by frontal cortex may be the white matter inputs to the striatum that result in reward dependence behavior.

This indicates that the stage theories are true!! If one considers the sub-cortical responses to be immature and the cortical responses to be more mature than moving from novelty seeking focus to reward dependence focus is a move up the stages. What I propose is that each stage marks a movement from sub-cortical input reliance to cortical input reliance and also involves novel mechanisms and systems.

Thus, as per my theory, in the first stage of personality development, or for the trait Harm Avoidance, the white matter connections implicated should be between sub-cortical regions and raphe nucleus ( the serotonin system).

In stage 2, or for trait Novelty seeking, the white matter tracts involved should be between cortical regions and Raphe nucleus (serotonin system). Also as the earlier serotonin system comes moer and more unedr cortical control, the second system based on dopamine becomes active but is under sub-cortical control. Thus, white matter tracts involving sub-cortical regions and striatum/ VTA should also be involved.

In stage 3, or for trait Reward Dependence, the white matter tracts should be between cortical regions and striatum/ VTA as the earlier dopamine system predominance us reigned in and a new system based on nor-epinepherine replaces it. This nor-epinepherine will be under sub-cortical control and white matter tracts from sub-coritcal regions to locus ceruleus should also be involved.

And this same scheme should go on for fourth (epinepherine), fifth (histamine/ melatonin), sixth, seventh and eighth stages/ personality traits.

All these are testable hypothesis and can be easily verifed. If verified, they can shed immense light on how perosnality develops and what do temperaments/ character strengths really mean.

Hat tip: Neurological correlates
Michael X Cohen, Jan-Christoph Schoene-Bake, Christian E Elger, Bernd Weber (2008). Connectivity-based segregation of the human striatum predicts personality characteristics Nature Neuroscience DOI: 10.1038/nn.2228

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Friday, December 05, 2008

26/11 and 'Beyond revenge'

26/11 has happened and I still write about  Science and Psychology.

It has been a week of introspection in which I have been questioning myself and whether by doing science blogging I am doing my bit as a responsible human being. Perhaps I will move on. But while I'm at science blogging let me discuss the topic about which the science blogosphere has been relatively silent.

Today, I have started reading Michal McCullough's "Beyond Revenge" and I want to discuss ideas from it. The decision to read the book at this juncture stems from the immense feelings of outrage that have been seething within and paradoxically without any overt war-mongering desires or ill-will towards the state that continue to let its soil be used for terrorist activities. Of course forgiving the citizens of that state was never an issue for the ordinary citizens do not foment violence and wars- it is the state or the alleged 'non-state' actors that are the real culprits; but I strangely feel a desire to forgive even them and give them a  second chance. But I cannot just forgive and forget. at least not this time. This time the world has to change to create the conditions whereby forgiveness is the norm and revenge an exception.

But let me not digress. Let me go straight to reviewing "Byond Revenge" . I have just read the introduction and the first chapter so let me share with you Mculloughs main thesis.

As per him there are three angle or truths to the revenge story:

  • Truth #1: The Desire for Revenge Is a Built-In Feature of Human Nature
  • Truth #2: The Capacity for Forgiveness Is a Built-In Feature of Human Nature
  • Truth #3: To Make the World a More Forgiving, Less Vengeful Place, Don’t Try to Change Human Nature: Change the World!

I've decided to the last, viz change the world, but perhaps not in exactly the same way that Michale may have intended. Let me elaborate what Michael means by the three truths:
The desire for revenge isn ’ t a disease to which certain unfortunate people fall prey. Instead, it’s a universal trait of human nature, crafted by natural selection, that exists today because it was adaptive in the ancestral environment in which the human species evolved .
I believe it is important to pause here and think over whether the perpetrators of 26/11 were themselves pathological or just normal ordinary people subjected to un-normal propaganda and state help to turn into monsters.

Its also important to acknowledge our own feelings of anger and outrage as vengeful feelings towards those who indulge in such heinous crimes; but it is heartening to note that Indians have largely turned their anger into constructive channels - towards lapses in security and towards insensitivity and callousness of politicians. It is heartening to note that the anger and revenge has not been mistakenly directed towards the citizens of a state or towards a community. I salute my fellow Indians for what they have done with their feeilngs of outrage and revenge.

Next truth Micahel elaborates as follows:

The capacity for forgiveness, like the desire for revenge, is also an intrinsic feature of human nature — crafted by natural selection — that exists today because it was adaptive in the ancestral environment in which the human species developed .

Forgiveness as per him is normally activated with friends and family; but India has always thought 'vasyudhev kutumbkam' or the 'whole world is my family'. India perhaps has been an epitome of forgiveness and perhaps will rightly remain so. I'm not just talking about India as a nation-state, I am talking about India as a civilization which has a unique honor of never committing aggression or getting involved in a war unprovoked. India has absorbed all erstwhile aggressors in its fold and today everyone lives as one community- one nation- one family. No heinous acts of aggression and terror make Indians turn towards each other. The need for that forgiveness instinct to continue is perhaps the greatest today. And believe me when I say that the common Indian citizen, still has no hard feelings towards the state who's soil is being used to foment terror on its territory.

The next truth he talks about is:

To forgive a stranger or a sworn enemy, we have to activate the same mental mechanisms that natural selection developed within the human mind to help us forgive our loved ones, friends, and close associates. To encourage more forgiveness in our communities, and on the world stage, we must create the social conditions that will activate those mechanisms .

This is what he means by changing the world. Creating conditions such that even enemies/ strangers seem like friends. Its heartening to note that partly as a result of state initiative, but largely due to initiative of non-state actors in India, like the media, we have been successful in creating a 'world' in which the ordinary citizen of Pakistan is not seen as an enemy. TV programs like 'the great Indian laughter challenge' on Star One have been able to make the ordinary Indian realize that there is much more in common that he shares with the Pakistan citizen than just a sub-continent. These non-state actors of my country, be it the film and music industry or NGOs have been working to foster stronger ties and the results are for all to see. For the first time, I do not hear war cries towards Pakistan , just a desire to eliminate the terror camps operating on foreign soil perhaps by very targeted and specific strikes. Is that asking too much? Is ensuring one's safety and taking preventive measure condemnable and will still be viewed as punitive and vindictive action by western and Pakistani media. Only time will tell whether the non-state actors in west and Pakistan have been creating their 'world' as per what template.

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