Some of the most important distinctions among memory systems in humans have been derived from the careful analysis of behavior of amnestic patients. The data clearly shows that working memory and long-term memory are two distinct mechanisms that the brain uses to preserve information after a stimulus has come and gone. Patient data has also allowed to delineate the difference between multiple long-term memory systems - most importantly a declarative memory system which is largely responsible for conscious memory, and a set of skill-based memory systems that are largely unaffected in amnesia. Controlled animal studies have helped to pinpoint the exact mechanisms underlying these memory systems.
