British scientists have discovered two neurons in men's brains which make them prioritise seeking out sex above all else – including food. Researchers discovered the two extra neurons that they had never noticed before in a worm species, known as Caenorhabditis elegans, even though the scientists were certain that they had mapped out the neurological being of this species in its entirety.
"It is a bit of a shock," says Richard Poole, a developmental biologist at University College London, who has called the neurons MCMs – "mystery cells of the male". Co-author Professor Scott Emmons, from the Departments of Genetics and Neuroscience at Albert Einstein College of Medicine, added: "Though the work is carried out in a small worm, it nevertheless gives us a perspective that helps us appreciate and possibly understand the variety of human sexuality, sexual orientation, and gender identification.
"Although we have not looked in humans, it is plausible that the male human brain has types of neurons that the female brain doesn't, and vice versa. This may change how the two sexes perceive the world and their behavioural priorities."
The report, published in Nature, says that it is proof that there is a difference in the way male and female brains are hardwired. The team made this discovery with the species of worm, which has no female gender – just male and hermaphrodite which carry sperm and can impregnate themselves – by conditioning them to not like salt by associating it with starvation.
They then added potential mates to a salted arena. Over time, they noted that while the hermaphrodites would look for the nearest exit to escape from the salt, the males would travel towards the hermaphrodite, despite the presence of salt. This led the scientists to the conclusion that the sex trigger was stronger than the starvation trigger.
Senior author Dr Arantza Barrios of UCL's Cell and Developmental Biology department, said: "Areas of the brain involved in learning display sex differences in many animals, including humans, but how these differences directly affect behaviour is not clear. We've shown how genetic and developmental differences between the two sexes lead to structural changes in the brain of male worms during sexual maturation.
"These changes make male brains work differently, allowing males to remember previous sexual encounters and prioritise sex in future situations."