Meet the Brain's Timekeepers

There are minutes and hours of our lives in which nothing happens, and these don't seem on the surface to be very challenging for our memories. At least, they make for succinct stories: "I waited 20 minutes for the doctor to come in." "I tossed and turned for hours last night." But how do we know it's been hours? How do we represent these chunks of lost time in our memories, accounting for all the empty minutes without actually losing them? Researchers at Boston University think they've found the answer. Buried in the brain's memory center, "time cells" tick away the moments like the second hand on a clock.