How do neurons connect? How do you work together to make decisions, express emotions, and raise awareness?
A complex map produced by a Johns Hopkins University mathematician and computer scientist could put us very close to the answer to these questions.
Marta Zlatic joined an international team of neuroscientists to create this map, which represents the learning and memory center of the fruit fly larva brain, a first step towards mapping how all animal brains function. The scientist has stored more than twenty thousand hours of black-and-white video, and the images are helping to answer one of the biggest questions in modern neuroscience: how brain circuits create behavior.
The part of the brain of the fruit fly larvae assigned in this project includes approximately 1,600 of the 10,000 neurons contained in the entire brain of a larva. The adult fruit fly brain comprises roughly 100,000 neurons, and the leap in complexity to mammals is even greater. The human brain contains eighty-six billion to one hundred billion neurons.
Map analysis reveals connection patterns between six types of neurons that had previously been misinterpreted or were entirely unknown , contributing to a better understanding of how this portion of the fruit fly larval brain functions. The challenge is such that we can compare it to trying to identify all the relationships of all the parts of a complex electrical network.
Closer to a full understanding of the brain
But understanding even the simplest of circuits presents a number of challenges. These vary in arrangement and function from animal to animal. It becomes difficult to fix a function to a circuit. Also, the wiring alone does not fully explain how the circuits generate the behavior . Other factors, such as hormonal ones, have to be considered.
However, scientists are beginning to detect patterns in simple circuits that can operate in more complex brains. “This is what we hope,” says Willie Tobin, a neuroscientist at Harvard Medical School in Boston, Massachusetts: “that we can find general principles that can help us understand larger systems .”
The project could also serve as a guide as scientists pave the way toward understanding the brain and ultimately toward the complex web of connections between neurons in mammalian brains . The part of the brain of the fruit fly larva used in the study roughly corresponds to the cerebral cortex in mammals.
In recent years, new tools and techniques for tracing the brain’s connections have brought us ever closer to a more precise understanding of how the brain works. What’s more, the resulting neural network diagrams are producing surprises; showing, for example, that a brain can use a network in multiple ways to create the same behaviors.
References:
The complete connectome of a learning and memory center in an insect brain. Katharina Eichler, Feng Li, Ashok Litwin-Kumar, Youngser Park, Ingrid Andrade, Casey M. Schneider-Mizell, Timo Saumweber, Annina Huser, Claire Eschbach, Bertram Gerber, Richard D. Fetter, James W. Truman, Carey E. Priebe , LF Abbott, Andreas S. Thum, Marta Zlatic & Albert Cardona. Nature 548, 175–182 (August 10, 2017). Doi: 10.1038 / nature23455
Image: Daniel Hertzberg
