In a first, a large, international team led by multiple labs at Harvard Medical School and Princeton University has published a complete wiring diagram of all the connections between neurons in the central nervous system of an adult fruit fly.

The work allows researchers to begin to study how the brain and body interact to carry out complex behaviors such as walking and flying. It also empowers deeper investigations into the basic principles of how nervous systems work.

"We can see all of the neurons and their connections as a complete unit for the first time and ask, "What do we learn from that?'" said study co-senior author Rachel Wilson, the Joseph B. Martin Professor of Basic Research in the Field of Neurobiology in the Blavatnik Institute at HMS.

The highly detailed diagram of neural connections—known as a connectome—adds a map of the fruit fly's spinal cord equivalent, called a nerve cord, to a previously published connectome of the fly brain.

"It is really important to have a central nervous system connectome that is as complete as possible so we can link up the brain and body and start thinking about behavior holistically," said study co-senior author Wei-Chung Allen Lee, associate professor of neurobiology at HMS and HMS professor of neurology at Boston Children's Hospital.

In analyzing the connectome, the team found that many fruit fly behaviors are controlled by local neural circuits in the body parts that are involved, rather than by a central hub in the brain.

The entire connectome is now freely available online so that other scientists can use it to propel neuroscience research.