Scientists have achieved the first complete mapping of every connection within the brain and nerve cord of an adult male animal. This 'connectome' provides a wiring diagram of 166,700 neurons and millions of connections in a male Drosophila, commonly known as a fruit fly.
The findings, co-led by scientists at the Medical Research Council (MRC) Laboratory of Molecular Biology (LMB), are anticipated to offer new insights into the neural mechanisms that influence behaviour. The complete map is crucial for tracing entire circuits from sensory input to motor output.
The study, published in Cell, revealed that approximately 95% of brain cells are shared between sexes. However, the differing 5% could potentially drive distinct behaviours, such as courtship in males and egg laying in females. Researchers hope this will help understand how genetic differences translate into variations in brain wiring and behaviour.
To create the map, a male Drosophila central nervous system was cut into 66 pieces and imaged using seven electron microscopes over a year. Artificial intelligence was then used to stitch these images into a 3D map, and advanced software tools were developed to annotate the brain map with cell types.