How newly discovered brain cells have made us rethink the human mind

IT IS strange to think that we still don’t know what our brains are made of. Yet, despite decades of research and the development of high-tech scanning techniques, that is the truth. Sure, we know the basics. The average human brain weighs approximately 1.4 kilograms and has the consistency of soft tofu. It is made up of two general cell types: neurons, which do the thinking, and glia, which support them. But beneath this simple description lies a mind-boggling complexity – a complexity that continues to surprise even neuroscientists.

Everyone knows neurons, the cells that send electrical impulses between different areas of the brain. Your brain contains around 86 billion of them and they come in many different varieties depending on their shape, function and properties. But there is still a lot we don’t know about them. Take rosehip neurons, which were discovered in 2018. Named for their shape, the cells seem to damp down the electrical activity of other neurons. Intriguingly, there is no equivalent cell in mouse brains, despite the fact that mice tend to have analogues of other human brain cells. We don’t really know much about what they do in the human brain, says Rebecca Hodge at the Allen Institute for Brain Science in Seattle, Washington, who was part of the team that discovered the cells.

Glia, which also number about 86 billion in the human brain, are even more difficult to pin…