How the Brain Keeps Its Memories in the Right Order

It began about a decade ago at Syracuse University, with a set of equations scrawled on a blackboard. Marc Howard, a cognitive neuroscientist now at Boston University, and Karthik Shankar, who was then one of his postdoctoral students, wanted to figure out a mathematical model of time processing: a neurologically computable function for representing the past, like a mental canvas onto which the brain could paint memories and perceptions. "Think about how the retina acts as a display that provides all kinds of visual information," Howard said. "That's what time is, for memory. And we want our theory to explain how that display works."