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The most comprehensive brain cell atlas to date

Natasha Kumar By Natasha Kumar Nov20,2023

Efforts by international researchers provide new insight into what makes the human species unique.

The most complete atlas of brain cells to date

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Artistic illustration of neurons in the human brain

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A veritable atlas of human and non-human primate brain cells is presented in a series of 21 studies published in the journals Science, Science Advances and Science Translational Medicine (New window) (in English).

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Three-dimensional images of neurons reconstructed from slices of living brains. The diversity of colors and shapes represent the wide variety of neuron subtypes that make up the human brain.

The work begun in 2017 was carried out as part of the BRAIN (for Brain Research through Advancing Innovative Neurotechnologies) initiative headed by the National Institutes of Health (NIH) in the United States. Canadian neuroscientist Jesse Gillis of the University of Toronto participated in this international effort.

The brain is certainly the most complex organ in the body. We are talking about more than 100 billion neurons. It is often compared to the number of stars in the galaxy, which is quite impressive, says Professor Martin Parent, of the CERVO Research Center associated with Laval University, who did not participate in the work.

This work has also made it possible to identify numerous new types of neurons, these cells which use electrical signals and chemical substances to process information.

In addition to the neurons, there are glial cells, twice as small but twice as numerous, which are essential to the functioning of the brain since they play a supporting role. The latter occupy an equivalent volume in the brain, and the present work has also identified new ones.

All these neurons and cells are connected in a way very precise with each other and form very complex networks, notes Professor Parent.

The question we always ask is whether the The human brain will one day understand itself! It's still an important challenge.

A quote from Martin Parent, CERVO Research Center

And the answer begins to emerge draw.

New studies report thousands of different brain cell types throughout the brain. For many parts of the brain, this complexity and variety had never been described before, explain researchers from the Allen Brain Institute, who participated in the work, in a press release.

The atlas makes it possible to characterize 3,313 cell types in the human brain, in some cases revealing characteristics that distinguish it from other primates.

This draft of the Map of human brain cells helps describe their shapes, locations, electrical activity patterns, and genetic characteristics. Its creation was made possible thanks to recent technologies that make it possible to examine millions of human brain cells taken from cadavers or during biopsies.

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A researcher holds a slice of a human brain donated to research following death of a person.

Professor Parent judges that this type of initiative carried out using human brains – and not animals – is very important because of the many differences between species. But working with the human organ still brings its share of challenges, since there is a lot of variability between individuals.

At CERVO, we work with a bank of brains donated by people after their deaths. This gives a still image, a photograph, at the moment of death. […] And the brains of animals used in research are very different from those of humans in terms of cellular composition, then organization of the brain.

A quote from Martin Parent, CERVO Research Center

By observing many brains, we can get an idea of ​​a so-called “normal” organization. We can then go and see what is happening in certain pathologies, to be able to detect changes, adds the researcher.

Generally speaking, humans share the same brain structure, but genetic and environmental factors also influence brain development and function.

Each person’s organ reflects their unique journey and life experiences. Thus, better understanding how all cell types behave and interact with each other in a healthy brain will – eventually – help neuroscientists to better understand the cell types associated with the diseases that develop there and to identify the corresponding cells in the model animal.

If we find certain generalities similar from one brain to another, such as the thickness of the different cell layers or the types of neurons present in the different regions, there are notable differences between brains visible at the naked eye, notes Professor Parent.

For example, On the surface, the cerebral cortex is arranged differently from one individual to another.

A quote from Martin Parent, CERVO Research Center

If we are moving towards creating an overall portrait of the normal, healthy brain, we must still remain cautious, since individual variability will always be observed. For example, a simple magnetic resonance imaging scan reveals different ways of working in healthy brains from one person to another. People use their brains differently to answer the same problem, notes the professor.

The accumulation of reliable and precise data will certainly make it possible to create a "kind of map of the brain" accessible to all researchers, whose level of precision will improve over the years.

A quote from Martin Parent, CERVO Research Center

One of the studies makes it possible to characterize the organization of brain cells specific to Homo sapiens in relation to non-human primates, a term which designates all species of the order of primates which are not members of the genus Homo.

For example, they show in particular that the neurons of chimpanzees more closely resemble those of gorillas than of humans, despite the fact that chimpanzees and humans have a more recent common ancestor.

One ​​of the studies also established that all cell types present in the human brain are also found in chimpanzees and gorillas. However, other work carried out in the past suggested that the human organ had distinguished itself during evolution by developing new types of cells.

However, within these cells, researchers discovered a few hundred genes that became more or less active in humans than in other apes.

It's really the connections – the way these cells communicate with each other – that differentiate us from chimpanzees, explains neuroscientist Trygve Bakken of the Allen Brain Institute, who participated in the primate studies, in a press release.

In addition, the Allen Brain Institute team discovered that a number of the genes that distinguish humans are involved in the development of the synapses that connect neurons between them.

This atlas allows us to better understand the cellular components of the brain, their number, their locations and the way in which they connect. It will make it possible to better explain how diseases such as Alzheimer's and schizophrenia develop, but also to target treatments based on cells.

The Understanding the human brain at such resolution will not only help scientists determine which cell types are most affected by specific mutations that cause neurological diseases, but it will also provide a better understanding of who we are as of any kind, notes the BRAIN Initiative press release.

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Natasha Kumar

By Natasha Kumar

Natasha Kumar has been a reporter on the news desk since 2018. Before that she wrote about young adolescence and family dynamics for Styles and was the legal affairs correspondent for the Metro desk. Before joining The Times Hub, Natasha Kumar worked as a staff writer at the Village Voice and a freelancer for Newsday, The Wall Street Journal, GQ and Mirabella. To get in touch, contact me through my 1-800-268-7116

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