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Posts Tagged ‘personality’

Probably not … but perhaps genes that predispose to certain personality or cognitive traits that help/hinder our ability to form stable social bonds.

“Several demographic variables including marriage, having siblings and children and educational attainment explain part of the variance in loneliness. Genetic factors, both additive and non-additive, explain about 37% of the variance.”

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personality1With more and more genes being directly associated with personality or as moderators of correlations between personality and brain structure/function (here, here, here, here) it was fun to try out the latest online “big-5 personality profiler“.

10 mins of self-reflective fun.  My profile displayed at left.

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Flash circuit

Image by cibomahto via Flickr

A recent paper from Andreas Heinz and colleagues (doi: 10.1038/nn2222) provides more neuroimaging evidence in humans for a a circuit that regulates our responsivity to stimuli that evoke emotional responses.  The basic circuitry involves the amygdala (a place in the brain where emotional memories are registered), the prefrontal cortex (a part of the brain that is involved in making decisions and assessing threats) and the cingulate cortex (a place in the brain where expectations are compared to sensory inputs & outgoing responses).  These 3 brain regions are interconnected in a loop through various synaptic contacts and the responsivity of these synapses can be modulated by neuomodulators such as dopamine, serotonin and noradrenaline.  It turns out, that several neuroimaging studies have begun to demonstrate that this (relatively) simple circuitry underlies human personality and temperament. In the Heinz study, the level of dopamine that was released into the amygdala was correlated with levels of functional activation to emotional stimuli as well as a dimension of temperament known as negative affect.

I recall once having taken the Meyers-Briggs assessment in graduate school and had a blast comparing my results with my wife – who was almost my polar opposite. Now, the latest neuroimaging and imaging-genetic research has begun to explain the complexities of human personality in basic neural circuitry where genes such as 5HTT and MAOA ‘turn up’ or turn down’ the gain on various synaptic contacts in this circuit – leading to the immense, yet systematic variation in personality and temperament that makes our social lives so interesting.  As I navigate my way through marriage and parenthood, I’m often glad I took the personality test with my wife many years ago.  It always helps to see things from the other person’s perspective.  Now, as she obtains her 23andMe profile, perhaps we will begin to compare our genomes together – the ultimate form of marriage counseling !!  Click here for more personality tests.

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inside my brain
Image by TheAlieness GiselaGiardino²³ via Flickr

Every student can recall at least one stereotypical professor who – while brilliant – kept the students amused with nervous and socially inept behavior. Let’s face it, if you’re in academia, you’re surrounded by these – uh, nerds – and, judging by the fact that you are reading (not to mention writing) this blog right now – probably one of them. So, its natural to ask whether there might be a causal connection between emotionality, on the one hand, and cognitive performance on the other. Research on the neuromodulator serotonin shows that it plays a key role in emotional states – in particular, anxiety. Might it exert effects on cognitive performance ? In their paper, “A functional variant of the tryptophan hydroxylase 2 gene impacts working memory: A genetic imaging study“, (DOI: 10.1016/j.biopsycho.2007.12.002) Reuter and colleagues use a genetic variation a G to T snp (rs4570625) in the tryptophan hydroxylase 2 gene, a rate limiting biosynthetic isoenzyme for serotonin to evaluate its effect on a cognitive task. They ask subjects (who are laying in an MRI scanner) to perform a rather difficult cognitive task called the N-back task where the participant must maintain a running memory queue of a series of sequentially presented stimuli. Previous research shows that individuals with the GG genotype show higher scores on anxiety-related personality traits and so Reuter and team ask whether these folks activate more or less of their brain when performing the N-back working memory task. It turns out that the GG group showed clusters of activity in the frontal cortex that showed less activation than the TT group. The authors suggest that the GG group can perform the task using by recruiting less of their brains – hence suggesting that perhaps there just might be a genetic factor that accounts for a possible negative correlation between efficient cognitive performance and emotionality.

My 23andMe profile shows a GG here – nerd to the hilt – what will I use the rest of my PFC for ? Something else to worry about.

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The publication of positive genetic association results is always something to cheer about although most of us know that on a different day, with a different sample, the results could just as easily been flat. So when a meta-analytical paper appears that actually supports a previous finding, you have to savor the sweet joy of it. So it is that Marcus Munafo and colleagues under the leadership of Jonathan Flint – one of the best meta-analytical assessors in the biz – report that the “C” allele of rs1800955 in the dopamine d4 receptor (DRD4) gene (doi: 10.1016/j.biopsych.2007.04.006) survives an analysis of several dozen studies on genetics and personality. Although small, “The evidence from our final meta-analysis indicatest hat the true effect size of the C-521T polymorphism on novelty seeking and impulsivity traits, if genuine, may account for up to 3%o of phenotypic variance.” I, perhaps due to my “C” allele am excited !

MUNAFO, M. (2008). Association of the Dopamine D4 Receptor (DRD4) Gene and Approach-Related Personality Traits: Meta-Analysis and New Data. Biological Psychiatry, 63(2), 197-206. DOI: 10.1016/j.biopsych.2007.04.006

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