In PSYC 420 we're reading Memory's Ghost: The Nature of Memory and the Strange Tale of Mr. M. by Phillip Hilts. This book is about one of the most famous amnesiac patients ever studied, known in the literature as H.M. In an effort to reduce seizures, H.M.'s entire hippocampus was surgically removed. It was quickly discovered, due to H.M.'s devastating memory loss, that the hippocampus and surrounding structures are key in memory formation and retention. Without these crucial brain regions, H.M. was unable to form new memories. He was unable to recall anything outside of a minute or two window of time.
H.M.'s story is tragic, but it also helped to greatly advance our understanding of the neural basis of memory and the importance of memory to our identities.
Recently, researchers have been able to examine his brain in greater detail to survey the extent of surgical damage. See this abstract from PubMed.