In their new study, published online September 25, 2018 in Cell Reports the researchers focused on “de novo” mutations, or rare mutations that arise anew at conception, rather than being inherited from parents. They observed that these mutations tend to affect genes with a role in cell “polarity,” which is the process by which cells differentiate “top” and “bottom.” This is particularly important in the brain, where neurons must form with specialized information gathering and transmitting sides to function properly.