The Invisible Brain

The notion of dark matter, as the name suggests, conjures up a feeling of the ethereal and the mysterious. One probably first thinks of the hypothetical material that makes up 85% of the universe’s density. That is what came to my mind upon seeing a new paper expanding on a theory of the dark matter of the brain. The paper, published last month in Brain Structure and Function, aims to convince the reader that large swaths of neurons in the brain remain “silent” throughout the lifespan. These silent ensembles of neurons make up this so called dark matter.

Historically, this is not the first time a biological phenomenon has been given the label of dark matter. The Human Genome Project discovered that up to 98% of the genome is non-coding DNA — in other words, DNA that does not code for a protein. Even more, the glial cells that make up the majority of cells in the brain were once thought to be merely structural, essentially silent “dark matter” of the brain. We now know that even the non-coding regions of DNA perform cellular functions that scientists are still elucidating. And glial cells have been found to be integral to brain function.

The paper is by Saak Ovsepian, who has multiple academic appointments at more neuroscience institutes in Europe than any author I have ever seen. In the paper, Ovsepian describes a population of neurons in the brain that remain essentially silent —…