Astrocytes are the cells in the brain whose job it is to protect, nurture, rewire and even build new neurons. Your brain thinks with neurons, but it maintains itself with astrocytes. But new research suggests that astrocytes get ugly when things go bad.

Scientists at Stanford University have discovered that when astrocytes are activated by traumatic brain injuries or by diseases like Alzheimer’s, they go from protectors to attackers. They kill thousands of neurons around them in a running rampage that this research suggests is the primary vehicle for the long-term effects of TBI and Alzheimer’s.