The human brain is so complex that scientific brains find it difficult to understand. A piece of nerve tissue, the size of a grain of sand may be full of hundreds of thousands of cells associated with miles of wiring. In 1979, Francis Crick, the scientist who won the Nobel, concluded that anatomy and activity in a cubic millimeter of brainwater would forever exceed our understanding.
“It is not useful to ask for the impossible,” wrote Dr. Crick.
Forty-six years later, a group of more than 100 scientists has achieved this impossible, recording cellular activity and mapping of the structure in a cubic millimeter of a mouse-less than one percent of its full volume. Upon completion of this holder, they gathered 1.6 Petabytes of data-the 22-year-olds equivalent of high definition video.
“This is a milestone,” said Davi Bock, a neuroscientist at the University of Vermond, who did not participate in the study, published Wednesday in Nature magazine. Dr. Bock said that progresses that allowed to record a cubic millimeter of the brain that well calculated for a new target: mapping the wiring of the entire brain of a mouse.
“It’s completely feasible and I think it’s worth doing,” he said.
It has been more than 130 years since Spanish neuroscientist Santiago Ramón Y Cajal first pulled out individual neurons under a microscope, making their peculiar branched shapes. Subsequent generations of scientists have been processed many of the details of the way a neuron sends a voltage spike under a long arm, called the shaft. Each axis comes into contact with tiny branches or dendrites of adjacent neurons. Some neurons stimulate their neighbors at their own voltage spikes. Some quiet other neurons.
Human thinking somehow emerges from this mixture of stimulation and inhibition. But how is this happening a huge mystery, mainly because scientists were able to study only a few neurons at a time.
In recent decades, technological developments have allowed scientists to start mapping the brain as a whole. In 1986, British researchers published the circuit of a tiny worm, consisting of 302 neurons. In the following years, researchers mapped larger brains, such as 140,000 neurons in the brain of a fly.
It could eventually be possible for Dr. it may be possible for Dr. Crick? In 2016, the US government launched $ 100 million to scan a cubic millimeter of a mouse brain. The project – called Machine Intelligence by cortical networks or microns – was driven by scientists at the Allen Institute for brain science, the University of Princeton and the Baylor College of Medicine.
The researchers were reset in a portion of the brain of the mouse that receives signals from the eyes and rebuilding what the animal sees. In the first stage of the research, the team recorded the activity of the neurons in the area as it showed a mouse video of different landscapes.
The researchers then put the mouse brain and threw the cubic millimeter with chemical sclerosis. Then shaved 28,000 slices from the web block, recording a picture of each. The computers were trained to identify cell contours on each slice and to connect the slices together in three -dimensional shapes. Overall, the group mapped 200,000 neurons and other types of brain cells, along with 523 million nerve connections.
For Nuno Da Costa, a biologist at the Allen Institute and one of the leaders of the project, just watching the cells shaped on his computer screen was amazing. “These neurons are absolutely amazing – it gives me pleasure,” he said.
To understand how this neuronate was working, Dr Dr Da Da Costa and his colleagues mapped the activity recorded when the mouse looked at the videos.
“Imagine you are coming to a party that has 80,000 people and you can know every conversation, but you don’t know who is talking to whom,” Dr Dr Da Da Costa said. “And now imagine you have a way of finding out who is talking to whom, but you have no idea what they are saying. If you have these two things, you can tell a better story about what’s going on in the party.”
Analyzing the data, the researchers discovered standards in the wiring of the brain that had escaped the notice so far. They identified different types of inhibitory neurons, for example, which are only associated with certain other types of neurons.
“When you go to study the brain, it looks a bit hopeless – there are so many connections and so much complexity,” said Mariela Petkova, a biophysist at Harvard, who did not participate in the Microns project. “Finding wiring rules is a victory. The brain is much less dirty than people thought,” he said.
Many of the young researchers are now sinking into a larger work: mapping of an entire mouse brain. With a volume of 500 cubic millimeters, a complete brain will take decades or centuries to record with current methods. Scientists should find extra tricks to complete the project in a decade.
“What they already had to do to get here is heroic,” said Gregory Jefferis, a neuroscientist at the University of Cambridge who did not participate in the Microns project. “But we still have a mountain to climb.”
Forrest Collman, a member of the Microns project at the Allen Institute, is optimistic. He and his colleagues recently discovered how to make tiny thin sections from a whole mouse brain. “Some of these obstacles begin to fall,” Dr. Collman said.
But our brain, which is about thousands of times larger than a mouse, presents a much greater challenge, he added. “The human brain now feels like the spectrum of what is possible,” he said. “We won’t go there soon.”
However, Sebastian Seung, a neuroscientist at Princeton and a member of the Microns project, noted that mice and human brains are similar enough for researchers to collect evidence that could help them find medication to deal with psychological disorders effectively.
“Current methods of handling the nervous system are incredibly blunt organs,” Dr. Seung said. “You put on a medicine and goes everywhere,” he added. “But he is able to really get in and handle a cell type – that is precise.”
Efforts to map a whole mouse brain are supported by funding by a long -term program of National Institutes of Health called Brain Initiative. But the future of the effort is uncertain. Last year, Congress reduced funding to the brain initiative by 40 % and last month, President Trump signed a 20 % bail.
Dr. Bock noted that brain mapping efforts, such as the young, need years, in part because they require the invention of new technologies and software along the way.
“We need consistency and predictability of science funding to accomplish these long -term goals,” Dr. Bock said.
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