Scientists create the largest ever maps of cells in the human brain

The human brain consists of about 86 billion nerve cells, along with many other types of cells. They interact and connect in unique ways, creating distinct brain regions with specific functions. Unraveling the complex composition and interactions of these many cells may lead to new understanding of how the brain functions in health and disease and new tools to study the complex activities and functions of these cells.

To better understand the identities and roles of brain cells, NIH’s Brain Research by Advancing Innovative Neurotechnologies® (BRAIN) initiative has launched an international network of collaborating researchers called the BRAIN Initiative Cell Counting Network. It aims to create a comprehensive list of all the cells in the brains of humans, non-human primates and mice, including the cells’ locations, interconnections and activities. Examining brain cells across species can identify characteristics that are uniquely human and provide insight into which animals to study for various scientific questions. The latest findings were reported in a series of more than 20 papers published in Science, scientific achievements, and Scientific Translational Medicine on October 13, 2023

One paper examined three human brains to find over 3,000 types of brain cells – more than previously known. The team identified specific cell types in distinct clusters in different areas of the brain. These findings could help shed light on conditions known to affect specific areas of the brain, such as cancer or neurodegenerative diseases.

Researchers have created the most detailed cellular atlas to date of the adult brain. The atlas reveals information about each cell’s gene activity and epigenome—the changes in a cell’s DNA and chromosomes that alter genetic activity. The findings also show that in addition to variation between brain regions, there is variation between individuals. More people will need to be studied to fully understand the patterns of healthy and diseased brains.

Another paper compared the cellular and molecular properties of the brains of humans and several non-human primates: the chimpanzee, gorilla, macaque and marmoset. The scientists found that several hundred genes have patterns of activity in nerve cells that are unique to humans. These changes may help explain humans’ remarkable ability to adapt, learn, and change.

The other papers cover different aspects of the brain. One, for example, is investigating the role that inflammation may play during early brain development. Severe childhood inflammation has been linked to developmental disorders such as autism and schizophrenia. The researchers analyzed gene activity in the brains of children who died between the ages of 1 and 5. They compared the brains of children who died from inflammatory conditions, such as asthma or infections, with those who died from accidents. The scientists focused on the brain’s cerebellum, which controls muscle movement and cognitive functions such as language and social skills. They found evidence that inflammation can block the development of specific types of nerve cells in the cerebellum. The discovery could lead to a better understanding and treatment of developmental disorders that are linked to inflammation.

“This body of research represents a remarkable achievement in illuminating the complexity of the human brain at the cellular level,” said Dr. John Ngai, director of the NIH BRAIN Initiative.

“These new detailed cellular atlases of the human and nonhuman primate brain offer a basis for designing new therapies that can target the specific brain cells and circuits involved in brain disorders,” adds Dr. Joshua A. Gordon, Director of the NIH National Institute of Mental Health.