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Posts Tagged ‘Monogamy’

Flash circuit

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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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The Great Dictator
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The small neuropeptides oxytocin (OT) and arginine-vasopressin (AVP) are well known for their influence on promoting warm-and-fuzzy social behaviors in mammals. The G-protein coupled OTR and AVPR1a receptors are also the subject of much research in this area – particularly AVPR1a – since it shows differences in brain expression in polygamous vs. monogamous vole species, and also shows genetic associations with dysfunction in human social affiliation. In a recent foray into this line of research, Richard Ebstein and colleagues examine whether an individual’s willingness to give away a cache of money is related to genetic variation in the promoter of the AVPR1a. In their paper, “Individual differences in allocation of funds in the dictator game associated with length of the arginine vasopressin 1a receptor RS3 promoter region and correlation between RS3 length and hippocampal mRNA“, the researchers asked 203 college students to play the “dictator game” where, simply, one person gets a sum of money and can choose to keep it or give some of it away to the other player. Thats it. Give some of it away if you like, or just walk away with all of it, no questions asked & no consequences (your identity and the identity of the other player are masked). Amazingly, individuals actually DO give some of the money away (15% gave none of it away, 35% gave half away and 7% gave all – yes, all of it – away) … and more amazing still … those with longer stretches of microsatellite repeats at the RS1 & RS3 promoter sites in the AVPR1a gene, gave away significantly more money than individuals with shorter version of the repeats.

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Armpit
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“Hey, you with the smelly armpits, how about a date ?”

Ahhh, if only this were true ! Sadly, not. However, it would appear that females eschewing us slovenly males may doth protest too much. Recall the popular science lab where females rank their preference to the smell of sweaty t-shirts of unshowered male classmates. Typically, this lab involves the genotyping of a number of Major Histocompatibility (MHC) gene polymorphisms and comparisons that show females prefer the odor of dissimilar MHC genotype. There are, however, well known clusters of odorant receptor genes within the MHC gene super-clusters and these may provide a more direct link from odor to preference. Liza Gross describes related findings in her article, “A Genetic Basis for Hypersensitivity to “Sweaty” Odors in Humans,” where the dosage of an olfactory receptor gene OR11H7P correlated with sensitivity to the odorant isovaleric acid. Although OR11H7P is not located within the commonly assayed MHC super-cluster on human 6p, it is a sweet-smelling step toward understanding mechanisms of female choice.

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