In early October this year, Howard Hughes Medical Institute’s Janelia Research Campus in collaboration with Princeton University’s FlyWire group presented the biggest digital map of an animal’s brain that has ever been made.
The concept of the connectomes – maps of the neurons in an organism’s brain – was formed at the beginning of the 20th century; however, the technology needed to perform the mapping was only developed at the end of the century.
The first successful attempt was made in 2019, when Dr. William Schafer and PhD student Lidia Ripoll-Sánchez accompanied by other scientists mapped the brain of the C. elegans worm. While the worm is only one millimeter long, its brain has 301 neurons and over 30.000 neuropeptide interactions. In March 2023, after five years of work, a bigger map was introduced: the complete map of the brain of a larval fruit fly, containing 3.000 neurons and more than half a million synapses, connection points between neurons.
The newest advancement, the map of the brain of an adult Drosophila melanogaster (fruit fly) is a complex network of almost 140.000 neurons, and more than 54 million connections. The adult fruit fly is capable of performing a wide range of behaviors, such as learning from odors, making decisions, navigating and flying, and courtship.
To build the connectome, the brain of the animal was carefully dissected into 7000 layers. Afterward, the scientists in Davi Bock’s lab took 21 million images, sending them to an AI model built by the Seung lab to finalize the 3D model. The AI transformed those images into a labeled three-dimensional map. In addition to the AI model, all the results were proofread by scientists during the past five years, however, without AI, the project would have taken around 50 thousand years.
The Effect on the Development of Neuroscience
The map of the fruit fly’s brain is a big step towards mapping the human brain. From the size comparison perspective, the human brain contains 600.000 times more neurons and a much wider range of functions, making it much more complex. Moreover, AI’s technological capabilities are not yet developed enough to process data in such a capacity, which delays the process to at least a few years.
The brain is the central organ of the neuronal system, also known as the nervous system, which is a complex network of cells that controls our organism’s function. The billions of neurons and trillions of synapses are responsible for all the actions that humans are able to perform, including information processing, thought and emotion, and movement and coordination. Consequently, a malfunction in the synapses can damage the cognitive thinking, sensory, and motor systems and cause neurological disorders. A good example of such a disorder is schizophrenia, which can be caused by neurobiological factors, such as abnormalities in brain structure. Other examples are Alzheimer’s disease and Parkinson’s disease. While modern medicine can manage and relieve symptoms of these diseases, they are currently considered incurable.
A map of the human brain would not only contribute to the research and deeper understanding of the functions of the brain but would also enable scientists to find the sources of complex disorders. Furthermore, targeting these identified sources could lead to the development of new therapies. This milestone could be the kick-off point of the studies of ways to cure incurable diseases.
Featured Image Courtesy of Independent, 2024
