Scientists generally classify memories into two categories: declarative and non-declarative. Declarative memories are things you know you remember, like the color of your car or what happened yesterday afternoon. EP and HM have lost the ability to make new declarative memories. Non-declarative memories are the things you know without consciously doing them, like how to ride a bike or how to walk from your bed to your bathroom. Those unconscious memories don't rely on the hippocampus. They happen in completely different part of the brain. As EP and HM so strikingly demonstrate, you can damage one part of the brain and the rest will keep on working.