Differences in habit learning between male and female mice are due to their chromosomes, not to their sex hormones, reports a paper in the November 2007 issue of Nature Neuroscience. Most sex differences in brain and behaviour are attributable to the effects of hormones, but this work suggests that some sex differences may be caused by chromosomes through another pathway.
Jane Taylor and colleagues studied mutant mice with XY (male) chromosomes and ovaries, mutant mice with XX (female) chromosomes and testes, and normal male and female mice in a test of behavioural learning. The XX mice were faster to learn a food-reinforced habit than the XY mice, regardless of whether they had testes or ovaries, and even if they had been removed. Habit formation is implicated in the progression from casual drug-taking to addiction, which happens more rapidly in women than in men. Future studies of the mechanism of this effect may provide insight into such differences.
Jane Taylor (Yale Medical School, New Haven, CT, USA)
Abstract available online.
(C) Nature Neuroscience press release.
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