A dominant male mouse does not just turn a female on - he makes her brain grow. Just a whiff of his odour is enough to make her brain sprout new neurons, and this growth drives her to want to mate with him, new research has found.

Samuel Weiss at the University of Calgary in Alberta, Canada, and his colleagues exposed 8- to 10-week-old female mice to soiled bedding from males of the same age.

Two weeks later they found that the brains of females exposed to dominant male pheromones had grown significantly more new neurons in two key regions of the brain than those exposed to subordinate pheromones and control odours.

What is more, these females would then pick the dominant male over the subordinate when presented with a choice of mates. Females that had not grown new brain cells did not.

The researchers think the new neurons encode trace memories of dominant males. The two brain regions in which the growth took place were the olfactory bulb, which processes smell, and the hippocampus, which is involved in memory.

These have been hailed as main sites for neurogenesis across many species, but the two had not been linked to the same stimulus before, says Weiss.

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