According to MIT News, Matthew Wilson, a professor of neuroscience at MIT, and Kenway Louie, a graduate student in 2001, have studied the relationships between memory, sleep and dreams. They found that when rats were trained to run along a circular track for food rewards, their brains created a distinctive firing pattern of neurons (brain cells). The researchers repeated the brain monitoring while the rats were sleeping. Low and behold, they observed the same signature brain activity pattern associated with running whether the rats were awake or asleep. In fact, the memories played at approximately the same speed during sleep as when the rats were awake.
It is known that the hippocampus, the portion of the brain that collects and stores memories, is wired much the same way in all mammals. Professor Wilson says, “If you compared a hippocampus in a rat to a dog; in a cat to a human, they contain all of the same pieces.” He believes that as dogs sleep, images of past events replay in their minds, much the same way people recall experiences while dreaming. In people it is known that most dreams occur during REM (rapid eye movement) sleep, according to the National Institutes of Health. Dogs also experience periods of REM sleep. There may be muscle twitching during REM and, when one looks closely, rapid eye movements behind closed eyelids can often be observed. It is during REM sleep that behaviors thought to be associated with dreaming (legs paddling, twitching, vocalizing, etc.) are most commonly observed.
When we observe our dogs as they sleep, it’s just about impossible to imagine that they are not dreaming. Just like the rats studied by Wilson and Louie, it is tempting to believe that our four-legged best buddies are reenacting their recent experiences; playing at the dog park, sniffing in the woods, chewing on a treasured bone, and chasing squirrels.