The medial temporal lobe was identified as an important neural structure in human memory by the advent of patient H.M., who suffered from severe amnesia caused by bilateral medial temporal lobectomy. Dozens of neuropsychological study of H.M. led to the classification of human memory into declarative and non-declarative memory, as well as short-term and long-term memory. The medial temporal lobe subserves declarative memory and long-term memory. It also plays an important role especially in the process of memory consolidation. The psychological and neurological mechanisms of the consolidation process can be investigated through the study of retrograde amnesia and epileptic amnesia.