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asking questions about men and women by looking at teenagers

posted 3 Dec 2013, 01:57 by Sophie Scott   [ updated 3 Dec 2013, 02:19 ]

This are a few comments on this paper on sex differences in the human connectome, published in PNAS. Cor, ain't it been popular in the press though, guvnor.

1.     The participants are aged between 8-22yrs, and the analysis splits them into six groups (male and female groups, and three different age groups). Nonetheless, a parametric factor of age would seem absolutely essential and means the movement issues pointed out by @practicalfMRI are a real issue. This also seem problematic as the authors themselves suggest that here are sex-related differences in brain development (effects which they don’t find, I think, see below)

2.     The connectivity is base on parcellation of 68 cortical and 27 subcortical regions per subject, and these are used as the nodes for the DTI analysis. This is a very coarse grained analysis of the human brain and assumes that this level and anatomical structure of parcellation is the correct one to address brain connectivity.

3.     I can’t find any analysis of the effects which are found across both men and women, either as two groups or in terms of main age effects – i.e. results are described in terms of sex differences, not the regression results. This means that it’s hard to judge the meaning of the results – sex is important, but we know age is important, too. And other studies have claimed that age is even more important than sex. NB there is no age-by-sex interaction in the connection based analysis, which is surprising.

4.     What does it mean to say that the male brain is optomised for interhemispheric processing? There are great big structures in the brain which connect the left and right hemispheres – are we to assume that these are non-functional in males, like nipples?

5.     You might also assume that we’d get a hint of such processing differences in the clinical literature, but other than some diseases affecting men and women differently in terms of numbers, the effects of stroke, Parkinson’s disease etc. are the same for men and women.