Why do scientists study the fruit fly brain? Although the fly brain is much simpler compared to a human brain, it is still capable of performing complex tasks, like navigation, memory, and color detection. 

A brain is made up of different types of neurons, which have to be connected correctly to carry out tasks. These physical connections in the fruit fly brain were recently mapped in 3D. Scientists used machine learning algorithms to analyze ultrathin brain slices imaged under an electron microscope, and identified over 25,000 neurons and 20 million connections.

Now, a recent Nature study has added another dimension to this brain map. Scientists identified which genes are turned on or off in specific neurons over the course of fly development, from early pupae to adult, during which critical neuronal connections are made. 

One interesting discovery from this new ‘developmental atlas’ is that certain neurons die before the fly becomes an adult, possibly because they are only needed for establishing connections of other neurons. Moreover, a new type of cell was identified which is similar to a type of neuron found in humans that is essential for brain development.

Having a clearer picture of how gene activities allow neurons to connect with one another in the fly brain will also benefit researchers working on the vertebrate brain. Importantly, the resources generated from this study pave the way towards a better understanding of developmental disorders that originate from improper neuronal connections.