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On the wiring of female and male brains

The data in the study concerned are derived from a technique called 
diffusion tensor imaging (DTI), which estimates how water diffuses along 
white matter tracts in the brain. The big advantage of DTI is that it 
can be used in living humans. Its big disadvantage is that even at best 
it gives only a very low resolution and thus partial picture of possible 
connections in the brain, and DTI is also rather poorly validated 
against 'gold standard' anatomical tracing methods that are routinely 
used in animal experiments. Thus, of the billions of connections made 
via the white matter of the human brain, DTI detects a tiny fraction of 
a percent and the method only indicates hypothetical anatomical 
connections and not any function. As a reality check one should take the 
example of the nematode worm, C elegans, which is the only animal for 
which we have a complete map of every connection in its nervous system. 
It has 302 neurons, compared to 85 billion in the human brain, yet no 
neuroscientist (or journalist) can tell you what is in the mind of this 
worm. Our knowledge of the connections in the human brain is 
poverty-stricken by comparison, yet this has not stopped some 
neuroscientists from linking their hypothetical structures of human 
neural networks, derived from techniques like DTI, directly to complex 
psychological process, as in the paper under discussion. Worse still, 
the media reinterpret and amplify the scientists conjectures to build 
their own confection of irresponsible speculation that bears little 
relation to the original data, as the present case so ably illustrates. 
- K. Martin