As beautiful as it is complex – a male fly's brain
Scientists have managed to compare the fine detail of the brains of male and female flies for the first time, identifying differences they say explain male aggression, courtship and their singing of love songs.
The scientists in Cambridge mapped all 124 million connections of nerve cells in a male fly's brain, having done the same for a female fly two years ago.
The team are clear that the research won't explain differences between men and women because our behaviour is far more complex.
But the research could help scientists better understand human behaviour and conditions in which genetic differences affect brain wiring, such as autism and schizophrenia.
Prof Gregory Jefferis, of the Medical Research Council's Laboratory of Molecular Biology and University of Cambridge, who co-led the research, told BBC News that the breakthrough was "a really important new avenue in neuroscience", likening it to the invention of a powerful new telescope in increasing our understanding of the Universe.
"We have this amazing stuff in our heads that lets us do incredible things such as playing a sonata or solving a scientific problem. And this development could help our understanding of how those systems work".
The map was made by cutting the fly brain into 66 pieces, each of which was imaged by repeated rounds of scanning.
The fly's brain is as beautiful as it is incredible. It is the size of a pin head – yet in many ways – more efficient than a supercomputer and able to outsmart the smartest AI.
Jefferis' team and collaborators painstakingly analysed every nerve cell, every wire and every connection in a male fruit fly. They put them together into a 3D map of the brain and nerve cord and compared them to the earlier, female mapping.
They found that around 95% of the cells are shared between the male and female fly brains. But the remaining 5% are enough to drive quite distinct behaviours, according to Dr Isabella Beckett, who is joint first author of the scientific research paper published today in the Journal Cell.
"We were expecting to find differences, and we found them, and we're excited by what we got," she said.
The small differences they discovered can lead to big changes in behaviour.
In courtship, for example, the male tracks the female as she moves. The researchers have identified the brain circuits associated with that trait and found key differences in the wiring. The males have extra bits that should enhance his visual tracking.
There is an even bigger difference in the circuits associated with aggression. Males fight more often and so there is much more wiring associated with that behaviour than in females.
