“Brain training” games like Project: Evo have become big business, with Americans spending an estimated $1.3 billion a year on them. They are also a source of controversy.

Adam Gazzaley found that it does indeed appear to prompt older brains to perform like ones decades younger. (“Game changer,” the cover of Nature magazine declared when it published his findings last year.) Now Project: Evo is on its own twisty path — the Boston company that is developing it, Akili, which Gazzaley advises, is seeking approval from the Food and Drug Administration for the game.