Mental Time Travel

People can recall things that happened to them years ago. We can also contemplate what might happen to us in the future. This is what some psychologists refer to as mental time travel. The front of the brain gives us the ability to project ourselves into the future, while an area called the hippocampus in the temporal lobes helps us create memories. What would happen if we didn’t have a hippocampus?

To answer this question, we need to look at what happened to a man called H.M. in 1953 (people are not identifed by name in the medical literature). H.M. had severe epileptic seizures that originated in his temporal lobes. His doctors decided that the best course of treatment would be to give him a bilateral temporal lobectomy (they cut out the temporal lobes on both sides of his brain). At the time, the relationship of the hippocampus to memory formation was not know.

After the surgery, H.M. no longer had seizures but he had a unique memory problem. He could no longer remember things that happened to him. Here is an example – someone could come into the room and greet H.M., leave for a couple minutes and return, and H.M. would act as though it were the first time he saw the person. He was in an infinite present, so to speak. Yet, the surgery didn't destroy H.M’s memory completely. He was still able to learn simple procedural tasks. The procedure H.M. had isn’t performed much anymore since anti-convulsive medications have improved vastly since the 1950s.

The case of H.M. was important for furthering our understanding of how memories are formed. When we compare the brains of other mammalian species, we find that they have areas that are similar in cellular makeup to our hippocampus. These areas are referred to as “hippocampal formations” in other mammals.

So, what would it mean that other mammals have a hippocampal formation? It suggests that they might have memories of their past. Of course, we cannot prove this idea since we cannot ask an animal about what they remember. It’s an interesting thing to ponder, though. Your dog just might have memories of when she was a puppy.