One third of children who have autism spectrum disorder also have epilepsy. It's related to an autism risk gene. But scientists didn't know why the mutation, catnap2, caused seizures. Now scientists have discovered the mutation shrinks the neurons' dendrite arbors and synapses that enable brain cells to relay vital messages. The 'Calm down!' message gets lost in the brain, causing neurons to spin out of control. Drugs could soon be tested to reverse seizures, language delay and intellectual disability.