Researchers report they were able to ameliorate Fragile X syndrome symptoms after inserting the Fmr1 gene into the brains of very young transgenic mice that had been genetically engineered to lack this gene. When the researchers measured brain activity for signs of anxiety and hyperactivity in response to stimuli such as stresses and sounds, they found that the reactivation of the gene in these mice had led them to no longer show Fragile X syndrome symptoms.