Hundreds of neuroscientists built a ‘parts list’ of the motor cortex, laying groundwork to map the whole brain and better understand brain diseases.

Before you read any further, bring your hand to your forehead.

It probably didn’t feel like much, but that simple kind of motion required the concerted effort of millions of different neurons in several regions of your brain, followed by signals sent at 200 mph from your brain to your spinal cord and then to the muscles that contracted to move your arm.

At the cellular level, that quick motion is a highly complicated process and, like most things that involve the human brain, scientists don’t fully understand how it all comes together.

Now, for the first time, the neurons and other cells involved in a region of the human, mouse and monkey brains that controls movement have been mapped in exquisite detail. Its creators, a large consortium of neuroscientists brought together by the National Institutes of Health’s Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative, say this brain atlas will pave the way for mapping the entire mammalian brain as well as better understanding mysterious brain diseases — including those that attack the neurons that control movement, like amyotrophic lateral sclerosis, or ALS.

The atlas is described in a special package of 17 articles published today (October 6, 2021) in the journal Nature, including a single flagship paper that describes the entire atlas.

“In a human brain, there are more than 160 billion cells. Our brain has more than 20 times more cells than there are people in this world,” said Hongkui Zeng, Ph.D., Executive Vice President and Director of the Allen Institute for Brain Science, a division of the Allen Institute, and lead investigator on several BRAIN Initiative-funded studies. “To understand how a system works, you need to first build a parts list. Then you have to understand what each part is doing and put the pieces together to understand how the whole system works. That’s what we’re doing with the brain.”

The massive BRAIN Initiative-funded collaboration involved dozens of research teams around the country who worked together to complete a cell-by-cell atlas of the primary motor cortex, a part of the mammalian brain that controls movement. Combining more than a dozen different techniques to define brain “cell types” across three different species of mammals, the resulting open-access data collection is by far the most comprehensive and detailed map of any part of the mammalian brain ever released….