Are Men's brains better connected?
September 14th 2008 06:29
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FROM: Telegraph.co.UK
Men's brains are 'better connected'
By Roger Highfield, Science Editor
Last Updated: 1:01pm BST 09/09/2008
Men have higher levels of nerve connections in parts of their brain than women, according to a study that will renew hostilities in the long running gender war.
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Previous studies have revealed differences in the density of nerve cells and other brain features but none of these gender differences have been linked to behaviour or function in a very convincing way.
Now, Dr Lidia Alonso-Nanclares and Prof Javier De Filipe of the Instituto Cajal, Madrid, Spain; and colleagues there and at the Universidad Complutense of Madrid, used fresh brain tissue removed from epileptic patients during brain surgery to explore microscopic differences in the brain structure of men and women, revealing a consistent difference.
The authors of a study in the Proceedings of the National Academy of Sciences used an electron microscope to study the brain tissue and discovered that in the temporal neocortex, a key part which is involved in both social and emotional processes, located near the ears, among other skills, that men had a one third higher density than women of synapses - the junction between two brain cells that enables precisely tuned cell-to-cell communication.
However, men had more brain cells, though the excess was slight compared with the excess in the number of synapses.
Prof De Filipe said that the difference in synapses was "very consistent" and surprising, though he stressed that in other regions of the brain women may have more connections.
Other work said that the anterior commissure, which connects several regions of the frontal and temporal lobes, is 12 per cent larger in women than in men, for example.
There has been little attention to the anatomical differences between men and women at the level of the synapse, adds Prof De Felipe.
Although these differences contribute to the way men and women differ, he could not say exactly how, though he said there had been much speculation and hilarity in the lab about how this higher connectivity could contribute to male interest in sex and football, not least because the study was led by "two very clever women."
Because they team only studied four men and four women, since the main object of the study was to compare human brains to those of rats, mice and monkeys, the authors emphasise that more research is needed to understand how these differences influence brain function.
Brain function has been shown to differ between men and women in various respects.
Intelligence is not one of them. Much more convincing, says the team are studies that show differences that relate to spatial and language abilities, and whereas men excel in mental rotation and spatial perception, women perform better in verbal memory tasks, in verbal fluency tasks, and in the speed of articulation.
These differences are not thought to be a only consequence of the influence of sex hormones - oestrogen and testosterone - on brain organization during development but also of genetic factors.
Brain scans have found structural differences in the cortical volume of the Wernicke and Broca areas, involved in language, as well as in the frontal and medial paralimbic cortices, and in the thickness and density of the gray matter in the parietal lobes.
Women are smaller than men, on average, and tend to have smaller brains.
But Prof De Felipe points out that the intelligence of humans with brains weighing as little as half the average, may be normal or even above average. "There is not a clear correlation with the size of the brain," he says.
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