April 11, 2009

thinking about twins thinking alike

Yes, twins think alike. What's more, "Genetic Contribution to Variation in Cognitive Function: An fMRI Study in Twins" is way cooler than the title suggests, for two reasons. First, "variation" understates what they're measuring, which is more like different mental strategies – a difference in kind, rather than degree – ; secondly, participants were not just twins, but sets of three brothers: two identical twin brothers, and a non-twin brother. That third brother is crucial to the experiment, because he shares about 50% of his genes with the others, allowing an estimate of the heritablity of variation in mental strategies. 

Another great thing about the paper is the structure of the discussion section. The authors ask: 
If genes affect typical as well as atypical areas of brain activation subserving cognition, this raises three questions: (i) Are brain activations under genetic influence interpretable in terms of cognition? (ii) Are the two mechanisms for genetic influences on brain activity related to behavior? (iii) May genes affect neural networks that are highly individualized in nature?
And then they go on to address each of their three questions, in turn. I found this organization very helpful! Tell me what the questions are, then answer them. 

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