Researchers have uncovered a surprising molecular chain reaction in the brain that may play a role in some forms of autism. The study suggests that nitric oxide, a tiny signaling molecule normally involved in fine-tuning communication between brain cells, can sometimes trigger a cascade of changes inside neurons. When nitric oxide activity rises, it can alter a protective protein called TSC2, weakening an important cellular brake and allowing the mTOR pathway, which controls growth and protein production, to become overactive.