H.M.'s Brain and the History of Memory In 1953, radical brain surgery was used on a patient with severe epilepsy. The operation on "H.M." worked, but left him with almost no long-term memory. H.M. is now in his 80s. His case has helped scientists understand much more about the brain.

What type of long term memory was intact in HM?

HM had his long term memory impaired and suffered from retrograde and anterograde amnesia. His short term memory was intact as well as his procedural memory. He could learn the Match to sample task, the Mirror-Drawing task and the Incomplete-drawing test. You just studied 19 terms!

Did HM have implicit memory?

His very short-term memory was intact and he could also form implicit memories: for example, after several practice sessions H.M. improved at mirror drawing (in which he had to draw a star, but could only see his hand in a mirror), despite never remembering the practice sessions!