Researchers map neural networks in fruit fly brains

Press release

Wednesday October 2, 2024

The NIH's milestone in brain research will help us better understand processes in larger animals.

Neuronal diagram of the brain of an adult fly. The brain of an adult fly contains 139,000 neurons and more than 50 million synapses. Tyler Sloan is a student at Princeton University

The National Institutes of Health supported a team of scientists who created the first map of neural connections in the brain of the house fly. This map is a wiring diagram, also known as a “connectome,” and it is the most complete connectome ever made for an adult animal. The work provides important information about how the brain is wired and what signals are responsible for proper brain function. The study details more than 50 million connections between 130,000 neural cells. It is one of nine papers in the journal Nature.

The tiny fruit fly has been used as a model to understand behavioral biology for many years, said John Ngai Ph.D., director of The Brain Research Initiative: Advancing Innovative Neurotechnologies(r)Or The BRAIN Initiative (r)from the NIH. This milestone provides researchers with a set of new tools to understand how circuits in the brain influence behavior. It also serves as a precursor to ongoing BRAIN-funded efforts to map connections between larger mammalian brains and the human brain.

This map identifies the different types of cells in the fruit fly brain, including synapses, or chemical connections between neurons. The map also provides insight into the neurotransmitters (chemicals like dopamine and serotonin) secreted by each neuron.

The researchers also developed a map that shows the projections of brain regions to each other, called a "projectome," which tracks the organization of the hemispheres and behavioral circuits in the fly's brain. This makes it possible to map brain circuits that control specific behaviors, such as the ocellar circuit that receives visual inputs and produces behavioral changes to orient the fly during flight.

The researchers also provided an annotated connectome of the flies, providing cell types, classes, and other information. This paper contains essential information for researchers using the fly connectome to understand brain physiology.

Fruit flies are capable of surprising us with their advanced cognitive abilities, behavior, and social interactions. This makes them an excellent candidate for the initial connectome project. They can, for example, form long-term memories, engage in social interactions, and travel great distances. The fruit fly connectome is now established. This methodology can be applied to rapidly create maps of similar complexity in larger-brained animals. The new map could serve as a guide to better understand the effects of various human mutations on brain connections.

The researchers took a fly connectome and created it. The complete brain of the fly observed under an electron microscope The researchers used a publicly available image and a computer to identify neurons, or “segmentation,” in the images. It’s not foolproof, so the researchers developed a system of computer tools to allow a large online community to review the segments and proofread them for accuracy. They could also collaboratively annotate cell classes and types. A consortium of fruit fly labs called FlyWire, which included scientists from around the world, did the proofreading to delineate and identify individual neurons.

Shelli Avenevoli, Ph.D., is the acting director of the NIH’s National Institute of Mental Health. She said that only 15 % neurons were reviewed in 2021. The fact that we opened up the review to other scientists studying the fruit fly brain dramatically increased the speed at which this connectome was completed.

You can find data analysis tools to analyze the entire fruit fly genome at https://codex.flywire.ai/. Researchers can interact with connectome data by visiting https://fafb-flywire.catmaid.org/The study was supported by the NIH BRAIN Initiative, a multidisciplinary collaboration between ten NIH institutes and centers This technology allows researchers to study the brain in unprecedented detail, both in health and disease, and improves how we diagnose, treat and prevent brain disorders.

Grants: MH117815, MH129268, MH120679, NS126935

Brain research using innovative neurotechnologies (r) The BRAIN InitiativeThe U.S. Department of Health and Human Services has registered the trademark "r."

The NIH BRAIN Initiative, a collaboration of 10 NIH institutes and centers that spans multiple disciplines, is uniquely positioned to make cross-disciplinary discoveries in neuroscience and revolutionize how we understand the brain. The BRAIN(r) Initiative has enabled researchers to gain unprecedented insights into the human brain in health and disease by accelerating the development and application of neurotechnologies. This will improve how we prevent and treat brain disorders. The BRAIN Initiative is a network of multidisciplinary federal and nonfederal partners whose current research portfolios and missions complement the goals of the BRAIN Initiative.

The National Institute of Mental Health: NIMH's mission is to improve the treatment and understanding of mental illness through clinical and basic research, and to pave the way for prevention, recovery, and cure. Visit the website for more information. NIMH Website.

The National Institute of Neurological Disorders and Stroke: NINDS NINDS is the leading funding agency for brain and nervous system research in the United States. NINDS's mission is to develop fundamental knowledge about the nervous system, brain, and other organs and to use this knowledge to reduce the burden of neurological disease.

The National Institutes of Health: The NIH is the medical research agency of the U.S. Department of Health and Human Services. It includes 27 institutes and centers. English The NIH, the national medical research agency, is the primary federal agency that conducts and supports basic, translational, and clinical medical research. It also studies the causes, treatment, and cures of common and rare diseases. Visit the NIH for more information about its programs. www.nih.gov.

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