Scientists have discovered a brain signal that can trigger a domino effect in some forms of autism. The study revealed a molecular chain reaction in the brain. Nitric oxide is a small signaling molecule involved in fine-tuning communication between brain cells. When nitric oxide activity rises, it changes a protective protein called TSC2. This weakens the important cellular brake. This allows the mTOR pathway, which controls growth and protein production, to become overactive. These changes inside neurons may play a role in the development of autism.