An international team co-led by the University of Cambridge has mapped every neuron in the male Drosophila fly’s brain and nerve cord, to produce a wiring map of the 166,700 neurons and the millions of connections between them.
Known in scientific terms as a ‘connectome’, this is allowing unprecedented insights into how the brain turns sensory input into sophisticated behaviour by allowing researchers to identify the chains of connected neurons deep into the brain.
Since the female Drosophila fly brain has previously been mapped - involving the same group, this new work allowed the researchers to directly compare male and female connectomes and pinpoint differences between them.
This revealed that neurons can reroute sensory information into sex-specific behavioural circuits to drive different male and female responses to the same stimuli. For example, male flies detect the smell of another male fly and respond with aggressive behaviour, whereas female flies respond to the same smell with courtship behaviour.
Understanding how a healthy brain works will also help researchers to better understand what goes wrong in a diseased brain.
This is the first full-scale connectome of an adult animal’s brain and nerve cord ever produced. The entire dataset now exists as a public resource, openly available as a reference and tool for other researchers.
The study, co-led by Dr Greg Jefferis’s group at the University of Cambridge’s Department of Zoology and MRC Laboratory of Molecular Biology, is published today in the journal Cell.
“This work is revealing how brains take the same sensory input and turn it into different behaviours depending on their sex. Seeing those differences is finally helping us to understand how sensory inputs drive behaviour – and to better understand the black box we call the brain,” said Dr Isabella Beckett, a researcher at the MRC Laboratory of Molecular Biology, one of the lead authors on the study.
“This full wiring diagram has massive potential - we’ve produced data that will enable all sorts of new studies into how the brain works and controls behaviours,” said Dr Philipp Schlegel, a researcher at the University of Cambridge and MRC Laboratory of Molecular Biology who was also involved in the work.
“This work has given us a blueprint that pinpoints the location of changes in male and female fly brains, and what types of cells are involved. It’s the first step in understanding the evolutionary processes that have led to these changes,” said Dr Marta Costa, a researcher at the University of Cambridge who was also involved in the work.
To generate the new connectome, collaborators at Janelia Research Campus sliced the nervous system of a male Drosophila fly into incredibly thin slices, then scanned these using high-resolution electron microscopy to produce millions of images depicting individual nerve cells and their connections. AI was used to build these images into a 3D map - reconstructing each neuron and identifying the synapses where they communicate. Human checks on the results required the equivalent of 44 years of human labour.
This work was carried out with collaborators at Janelia Research Campus, the MRC Laboratory of Molecular Biology and Google Research. It was funded primarily by UKRI MRC and the Wellcome Trust.
References
Berg, S. et al: ‘Sexual dimorphism in the complete connectome of the Drosophila male central nervous system.’ Cell, Sept 2026.
Three related papers are published concurrently by the team:
Tastekin et al: ‘From Sensory Detection to Motor Action: The Comprehensive Drosophila Taste-Feeding Connectome.” Cell, Sept 2026.
Hoeller et al. ‘The organization of visual pathways in the Drosophila brain.’ Cell, Sept 2026.
Rubin et al. ‘Networks of sexually dimorphic neurons that regulate social behaviors in Drosophila.’ Current Biology, Sept 2026.