HM case study

• After the removal of his hippocampus, HM had a severely impaired episodic memory. He could remember events from 10 years before the surgery, but could not have new memories, or retrieve them.
• HM's semantic memories were unaffected.
• Milner discovered that HM was able to trace a shape using a mirror image (difficult task) and improve at this skill over the course of a few days. However he had o conscious recollection of every doing this task.
• HM was able to use procedural memory to learn the skill, but his brain operation had damaged his declarative memory to consciously remember this experience.