You might not realize it, but you’re born with more brain cells than you know what to do with. Or at least more brain-cell connections. As you grow older, through childhood and adolescence, you get rid of the connections that aren’t being used to store information or to tell you which tie goes with that jacket.
For years researchers have known about this cellular pruning. But they didn’t know how it worked. Now scientists from the Stanford University School of Medicine report that it’s the immune system that carries out this critical brain maintenance. In fact, the same protein that helps gets rid of uninvited bacteria also eliminates unused neural connections. The findings appeared in the December 14 issue of the journal Cell.
This routine cellular maintenance is important for normal brain development. Mice that are missing this pruning protein wind up with disorganized, abnormal retinas. And mice that are prone to getting glaucoma make too much of the protein, particularly later in life—so connections in their retinas are destroyed when they shouldn’t be. Reigning in this overzealous pruning process could provide a treatment for glaucoma or for other diseases where neural connections are lost. But it probably won’t help you decide whether to go with the solid tie or the stripes.