According to the research team, the variations in the density of the synapses that connect neurons may help to explain differences in how men and women think.
Even though the intelligence levels are equal, women and men excel at different cognitive tasks.
But although brain size and neuron density differ between the sexes, these don't seem to correlate with cognitive differences. Therefore, Javier DeFelipe at Complutense University in Madrid, Spain, and colleagues counted the number of synapses instead, reports New Scientist.
The brain tissue they analysed came from the left temporal cortex, a region of the brain involved in emotional and social processing, of four women and four men with epilepsy. The tissue itself was healthy, having been removed to allow doctors to access underlying damaged areas.
The men had up to 52percent more synapses per brain "layer" in this region than the women.
While the effect of high synaptic density in the region is unknown, the team suspects that there may be other regions where women out-synapse men.
In any case, says DeFelipe, although different synaptic densities indicates different circuitry between men and women, men shouldn't get too cocky: the density of synapses in mice is greater than in humans.
The study has been published in Proceedings of the National Academy of Sciences.