Second complete map of a fruit fly brain completed

On Friday, researchers announced the completion of a map of every neuron in the brain of a male fruit fly. The “connectome” provides a tool that can accelerate neurobiology research. But it also provides an opportunity to do some science on its own, as the connectome of a female Drosophila had been completed earlier this year. The work also provided the team behind it the opportunity to refine tools that are likely to be applied to ever-more complex nervous systems, including (potentially) those of vertebrates.

The new work involved a collaboration between biologists at the Howard Hughes Medical Institute’s Janelia Research Campus and computer scientists at Google—both acknowledge that neither could have done the project without the other. Preparation of an entire brain for imaging at the necessary resolution requires a distinct set of skills, as does interpreting what those images indicate. But building a complete picture of the hundreds of millions of synapses in a brain as small as the fruit fly’s is a task that can’t be achieved by humans in a manageable amount of time.

The people behind the effort expect that in the long term, the effort will be worth it, as the connectome could give neurobiologists a valuable tool for understanding how the brain works.

Establishing a connectome

Our interactions with the world begin with sensory input—the neurons that register sound, light, touch, and more. From there, most brain activity involves neurons communicating with each other. This communication transforms the inputs into signals the rest of the brain can interpret, routes information to relevant processing centers, and often produces some kind of output, from forming a memory to moving a muscle.

All that processing is dictated by which neurons have connections to others. For example, the visual system does some basic recognition of its own before passing the results to the brain’s visual processing centers. If those centers detect something like text, they can use connections to the language centers to interpret it, and so on.