Mysterious New Brain Cell Discovered In Humans

What makes humans unique from other animals? Scientists may have found one of the possible answers: a new type of brain cell in humans.

The newly discovered neuron is still largely a mystery, but its absence in mice and other rodents highlight the unique nature of the human brain.

Discovering A New Brain Cell

In the study published in the journal Nature Neuroscience, a team of scientists introduce a new type of human brain cell. They call it the "rosehip neuron" due to the distinctly rose-like shape of the axon around the center.

The breakthrough discovery is the result of two teams — the Allen Institute for Brain Science in Seattle, United States and the University of Szeged in Szeged, Hungary — independently coming across the mysterious neuron and collaborating.

So far, it's a neuron that's only been found in humans and the authors have confirmed that it's not present in mice and other laboratory animals. Further research could explore its presence or absence in other animals.

"We really don't understand what makes the human brain special," Ed Lein, Ph.D., coauthor and an investigator at the Allen Institute, says in a statement. "Studying the differences at the level of cells and circuits is a good place to start, and now we have new tools to do just that."

Rosehip Neuron: What We Know

According to Live Science, scientists took so long to discover rosehip neurons likely due to the cells' rarity. It makes up around 10 percent of the first layer of the neocortex, which is linked to sight and hearing. This new type of neurons attach to pyramidal cells, an excitatory neuron.

Rosehip neurons join a class known as inhibitory neurons, which functions by stopping other neurons' activity in the brain. It's still unknown how exactly it affects the pyramidal cells or brain behavior, but the researchers found that rosehip neurons only attach to one specific part of their cellular partner. This suggests a very specialized manner of control.

"This particular cell type — or car type — can stop at places other cell types cannot stop," Gábor Tamás, Ph.D., coauthor and a neuroscientist at the University of Szeged, explains. "The car or cell types participating in the traffic of a rodent brain cannot stop in these places."

Implications In Medicine, Science

What they do know is that the rosehip neuron is not present in mice and other laboratory animals' brains. Even if it's not exclusive to people, it could be one of the very few cells that may exist only in the brains of humans or primates in general.

Tamás points out that rosehip neuron's absence in mice brain underlines how challenging it is to model human brain diseases in laboratory animals.

"Many of our organs can be reasonably modeled in an animal model," he says. "But what sets us apart from the rest of the animal kingdom is the capacity and the output of our brain. That makes us human. So it turns out humanity is very difficult to model in an animal system."

Tamás' team is already planning to examine postmortem brain samples of people with neuropsychiatric conditions to check if rosehip neurons are altered with diseases.