Darwin says it’s monkeys or chimpanzees. The evolution from single-cellular organisms to multicellular ones resulted in the birth of humans. Based on that, neuroscience says we are similar to many who come before us, contributing to the pathway of the rise of humans. One of them is fruit fly or Drosophila melanogaster.
Although the fruit fly is tiny with 350 microns of length, 250 microns of height, and 750 microns of width, it shares 60 percent of our DNA including learning skills, jet lag, and Down Syndrome. They also communicate to their romantic partners the way we do. They sometimes experience trouble in navigation, respond to dark and light paths, avoid predators, and find food like humans.
Like us, they can also get drunk and have a similar aging cycle. They get excited and stressed as they have similar neurotransmitters, glutamate, acetylcholine, and dopamine.
Several studies have been conducted on fruit flies to understand the human body’s functioning and received ten Nobel Prizes. These studies helped scientists identify many similarities such as the effects of caffeine on their sleep cycles.
In fact, on 20 February 1947, NASA sent a fruit fly into space when they decided to launch living beings there to determine the impact of rays on human beings. The scientists launched fruit flies from White Sands Missile Range on a V-2 Rocket. In 190 seconds, they covered 109 kilometers of altitude and returned to Earth alive and unharmed, confirming that humans can go to space too.
Since the early 1900s, scientists have been using fruit flies for research experiments. In 1901, an infamous scientist, Dr William Castle used fruit flies for the first time after he found that studying them was easier than guinea pigs. His single step paved the ground for other scientists to demonstrate key phenomena in the human body via this insect.
In the meantime, Thomas Hunt Morgan demonstrated that genes are present on chromosomes via fruit flies. This work led him to win the Nobel Prize in Physiology in 1933. In 2000, in the Berkley Drosophila Project, scientists sequenced the genome of a fruit fly completely, led by Dr. Gerry Rubin.
Focusing on behavior and the brain, in 2003, Jeffrey C. Hall, an American geneticist, expanded the research on the fruit fly brain that was already in concentration since 1970. Seymour Benzer started with a core focus on mutation and circadian rhythm, Jeffrey discovered the pigment-dispersing factor protein that controls circadian rhythms and found that it is located in small ventral lateral neurons. For this, he won the Nobel Prize in Physiology in 2017.
Expanding research further in neuroscience, in 2023, Michael Winding – computational neuroscientist, published a connectome of fruit fly larvae’s brain in Science. Co-authored by other researchers including Carey E. Priebe, the team found that larvae have 3016 neurons and 548,000 synapses. The team took more than five years to create the complete connectome.
This year, after a decade of research, on October 2, 2024, a group of scientists from Princeton University, published a research paper in Nature. They mapped the whole brain of the adult female fruit fly or connectome has 139,255 neurons and 50 million synaptic connections.
It was the collaborative effort of FlyWire, a group of scientists from 146 labs of 122 institutions, primarily from the University of Cambridge and the University of Vermont.
The project is inspired by EyeWire, a crowd-funded group of scientists that mapped the retina of a mouse in 2013. Because of tech limitations, they have utilized AI tools to collaborate with other scientists. In 2012, the group publically announced the project, inviting scientists to contribute. FlyWire is an extension of the old project that utilizes the latest advancements in AI.
Led by Sebastian Seung, a computer science and Evin neuroscience professor who was also part of EyeWire a decade ago, and Mala Murthy, a neuroscience professor and director of the Princeton Neuroscience Institute, the fruit fly project was a collaboration between Seung and Mala Labs and the Allen Institute of Brain Sciences.
In this project, the researchers sliced the brain into 7050 layers to take around 21 million photos of its brain in electron microscopy at Dervi Books Labs and Howard Hughes Medical Institute Jaelia Research Campus.
With the help of a Seung and Mala Labs-designed model, AI analyzed the images and traced every path of every neuron and synaptic connection to make predictions. During this phase, it made a few discoveries and predictions.
First, AI precisely predicted the neurons were activated due to touch and taste simulations. Unlike the regular pathway, AI found that information travels fast to the brain upon touch. Yet while moving to the brain, different factors affect the information such as mood, activity, and the stimuli giver.
Second, while constructing the anterior visual pathway, AI spotted the ocular circuit responsible for visual guidance to a fruit fly. To help in navigation, the insect has 50 compass neurons. Compass neurons are neurons that tile together deep in the brain within an ellipsoid body. These neurons effectively connect the ocular circuit with the eyes by sending information.
Third, AI identified that information flows to and from the brain through suboesophageal zone (SEZ). It receives information from all brain parts and sends signals to motor neurons.
AI speeds up the pace of this project by analyzing photos. Sebastian, a lead scientist in this project, said “It would take 50 thousand people years to complete the project without AI. The scientists proofread an AI model and compiled it to create a 3D map of a fruit fly brain.”
Discovery of new neurons in the adult fruit fly brain
Based on the information received, the team classified neurons into 8453 types out of which, they discovered 4581 new neurons. During this research, the scientists found out that they could stretch the neural wiring of the fruit fly up to 490 feet which is longer than the blue whale.
“The mapping of the adult female fruit fly brain will surely pave the way to understanding our brain.” Sebastian says “Anything about a brain that we truly understand tells us something about all brains. Now, moving further towards the main goal, scientists in the E11 lab aim to map the mouse brain and make the dream a reality soon.”
Understanding the human brain is the most challenging task as it is the most complex organ. However, the progress since last year with the development of connectomes makes scientists hopeful that soon there will be a cure for major neurological diseases.
References:
- https://www.smithsonianmag.com/smart-news/scientists-unveil-the-first-ever-complete-map-of-an-adult-fruit-flys-brain-captured-in-stunning-detail-180985191/
- https://www.theguardian.com/science/2024/oct/02/fruit-fly-brain-connections-wiring-diagram-neuroscience
- https://www.euronews.com/health/2024/10/06/scientists-produce-first-and-largest-brain-map-of-a-dead-fruit-fly
- https://news.berkeley.edu/2024/10/02/researchers-simulate-an-entire-fly-brain-on-a-laptop-is-a-human-brain-next/
- https://www.nih.gov/news-events/nih-research-matters/complete-wiring-map-adult-fruit-fly-brain
- https://www.princeton.edu/news/2024/10/02/mapping-entire-fly-brain-step-toward-understanding-diseases-human-brain
- https://www.science.org/content/article/complete-map-fruit-fly-brain-circuitry-unveiled
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