“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. Industry observers warn that snake-oil salesmen abound, and nearly all neuroscientists agree there’s very little evidence yet that these games counter the mental deficits that come with getting older. Gazzaley, however, is something of an outlier. His work commands respect from even the harshest critics. He spent five years designing and testing the sort of game play I had just experienced, and he 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. If it gets that government stamp, it might become a sort of cognitive Lipitor or Viagra, a game that your doctor can prescribe for your aging mind.

In recent years, neuroscientists have begun to map, in increasing detail, just what happens as the brain ages. The picture is bleak. Beginning in our late 40s and 50s, our working memory dims, and we lose the ability to juggle simultaneous tasks. It becomes harder to screen out distractions, to stay focused while reading or shopping. Processing speed — that is, the brain’s ability to react to stimuli — slows, which is one reason older people struggle to follow the speech of chattering children. Scientists have begun to trace the physical changes behind this decline. For example, the myelin sheathing that covers the brain’s white matter degrades, and the brain has a harder time coordinating its different regions engaged in a mental task. This dropoff has nothing to do with Alzheimer’s or dementia; this is normal aging in an otherwise healthy adult. “It’s a rough life, being a nervous system over 60 or 70 years,” says Jonathan King, who directs a cognitive-aging program at the National Institute on Aging.

Since Gazzaley began his career two decades ago, in his 20s, he has been fascinated by the puzzle of aging. Back then, neuroscience was in the midst of the “neuroplasticity” revolution, the discovery that the mature brain can change and evolve. Scientists used to believe that once you became an adult, your brain’s capabilities were fixed, like plaster. But in the 1990s and early 2000s, aided by new brain-scanning tools, they realized this wasn’t true. If you start doing something that taxes your brain in productive ways, forcing it to repeatedly engage declining skills — learning a new language, for instance — those skills get measurably sharper. The problem, of course, is that most of us are pretty lazy. We’re not often going to take up mentally difficult activities in our dotage.

Video games seemed like one possible shortcut. Researchers were discovering that playing them appeared to improve some cognitive abilities in children: Avid players were better at noticing visual stimuli and shifting the focus of their attention, the very tasks that old brains find difficult.

In 2005, Nintendo released Brain Age, a slightly tongue-in-cheek game that purported to “keep your mind in shape” through a blitz of visual quizzes — like the famous Stroop Effect test, in which the word “blue” is printed in black, for example, and you have to correctly name the font’s color. (Not as easy as it sounds.) The brain-training industry was born, and soon ads from companies like Lumosity were promising to “challenge your brain with scientifically designed training.” Posit Science, a company founded by the neuroscientist Michael Merzenich, produced BrainHQ games meant to improve capacities like your “useful field of view,” the scientific term for the width of your peripheral vision. (Yes, it too shrinks with age.)