The brains of animals are the most complex structures on Earth. The human brain contains about eighty six billion nerve cells, or neurons, and an estimated two trillion synaptic connections, where these cells interact with one another. Futurists speculate that it may, one day, be possible to make a complete description of a person’s brain and implement it on a powerful computer. Would this really “upload” the person’s mind and consciousness onto the computer? Nobody knows, and the possibility is still far beyond current technology. Neuroscientists, though, have made some progress in completely mapping much simpler brains. Their goal is simply to learn more about how brains work, using a variety of tools including computer simulation.

In 2024 a large international team of researchers announced a major new breakthrough; they had completely mapped the brain of a fruit fly. This brain is about the size of a poppy seed, but still contains, by their count, one hundred and thirty nine thousand two hundred and fifty five neurons, and more than fifty four million synaptic connections. After chemical treatments to fix and stabilize the tissue, the researchers sliced the tiny brain into seven thousand thin slices. They scanned each slice with a powerful electron microscope. The tendrils of many neurons snaked through multiple slices.

Aligning the images of all those neurons across slices required the use of artificial intelligence. Hundreds of people from more than fifty labs proofread the computer’s work to ensure the alignment was correct. The completed result of this monumental job was a computer based map of the fruit fly’s brain—the most sophisticated such brain map ever made.

Learn more

• Fruit flies are social butterflies
• Fruit Flies Love Alcohol
• Flies' Eyes And Human Eyes May Be Closely Related

Sources

Scientists have traced all 54.5 million connections in a fruit fly’s brain, Science News, https://www.sciencenews.org/article/fruit-fly-brain-connections-traced.

Largest brain map ever reveals fruit fly’s neurons in exquisite detail, Nature, https://www.nature.com/articles/d41586-024-03190-y.

Complete map of a fruit fly brain circuitry unveiled, Science, https://www.science.org/content/article/complete-map-fruit-fly-brain-circuitry-unveiled.

Tiny brain, big deal: Fruit fly diagram could transform neuroscience, The Guardian.com, https://www.theguardian.com/science/2024/oct/02/fruit-fly-brain-connections-wiring-diagram-neuroscience.

First map of every neuron in an adult fly brain, UK Research and Innovation, https://www.ukri.org/news/first-map-of-every-neuron-in-an-adult-fly-brain/.

Dorkenwald et al. 2024 Neuronal wiring diagram of an adult brain, Nature, 634:124-155. https://doi.org/10.1038/s41586-024-07558-y.

Schlegel et al. 2024 Whole-brain annotation and multiconnectome cell typing of Drosophila

Nature, 634:139-178. https://doi.org/10.1038/s41586-024-07686-5.