HM was able to recall most events from before

HM was able to recall most events from before his surgery, although there was a partial loss of earlier memories, which is referred to as retrograde amnesia HM became the subject of extensive studies into how memory works What he was unable to do Formula Focus was form new memories of what happened to him, what are now called episodic memory Episodic memory is autobiographical in nature, such as remembering riding a bicycle as a child around the neighborhood, as opposed to the procedural memory of how to ride a bike HM also retained his short-term memory, such as what is tested by the three-word task described above After a brief period, those memories would dissipate or decay and not be stored in the long-term because the medial temporal lobe structures were removed The difference in short-term, procedural, and episodic memory, as evidenced by patient HM, suggests that there are different parts of the brain responsible for those functions The long-term storage of episodic memory requires the hippocampus and related medial temporal structures, and the location of those memories is in the multimodal integration areas of the cerebral cortex However, short-term memory—also called working or active memory—is localized to the prefrontal lobe Because patient HM had only lost his medial temporal lobe—and lost very little of his previous memories, and did not lose the ability to form new short-term memories—it was concluded that the function of the hippocampus, and adjacent structures in the medial temporal lobe, is to move (or consolidate) short-term memories (in the pre-frontal lobe) to long-term memory (in the temporal lobe)

HM was able to recall most events from before