HM of Brenda Milner

Introduction

An individual known & studied for his profound anterograde amnesia after bilateral medial temporal lobectomy.

HM's learning ability:

• intact memory:
  • classical conditioning paradigms
  • pursuit rotor, bimanual, tapping tasks (motor learning)
  • testing habits, tower of Hanoi
  • incomplete picture tasks (evidence of savings) & priming tasks
  • remote memory & working memory are intact
• profound anterograde amnesia
  • cannot learn new tasks
  • varying degree of retrograde amnesia

Biographical information:

HM was born in 1926. Development was unremarkable. At the age of 7 years, he was knocked off a bicycle & rendered unconscious for 5 minutes. At the age of 10, he began to have seizures (petit mal seizures). At the age of 16, he had his 1st grand-mal tonic-clonic seizure. He finished high school, but the seizure frequency continued to worsen despite ECT therapy. Seizure frequency of 10 petit mal seizures/day & 1 grand mal seizures /week.

At age 28, in 09/1953, he underwent bilateral medial temporal lobectomy. Dr. William Scoville, a neurosurgeon performed the surgery. Dr. Scoville later described the surgery as "frankly experimental". After the surgery, seizure frequency drastically decreased & seizures were controlled with ECTs. He continued to have occasional petit mal seizures, but most of his grand mal seizures were well controlled.

His post-operative period was uneventful. He displayed adequate social skills without any change in personality. He was supposedly an extremely friendly & nice man. His verbal expression was 'better than normal'. Intellect was intact. Post- operative IQ was 112 vs 104 pre-operatively. The difference was accounted for by an improvement in arithmetic. He retained the ability to read, write, calculate & retained autobiographical information. He had a profound loss of sense of smell.

He underwent formal neuropsychological evaluation by Brenda Milner in 1955. His 1st reply to the questioning was: "It is March 1953 & I am 27 years old". Brenda Milner continued to work with HM for many years. She said that he never recognized her, despite seeing him for years on a nearly daily basis.

He had profound anterograde amnesia. In 1984 by S. Corkin remarks 'He did not know where he lives, who cares for him, or where he ate his last meal. His guesses as to the current year may be off by as much as 43 years.' In 1982, he did not recognize a picture of himself taken on his 40th birthday in 1966.

Some facts managed to be encoded & stored. Although he watched TV every night, he was unable to say anything about Watergate. However, he knew that Howard Cosell was a newsreader & he some- how learned that Archie Bunker, a TV character, called his son- in-law 'Meathead'. His vocabulary was frozen in the 1950s. He was able to acquire 'ayatollah' & 'rock 'n' roll'. On formal measures, his memory quotient was 67 (average 100 +/- 15). He cannot recall the Rey-Osterrieth complex figure despite accurately copying it minutes earlier. It did not matter if a memory task was words, paired associates, maze solutions or locations, he failed all - HM's forgetfulness was almost total.

However, HM's working memory was intact. HM was able to retain the number 584 for at least 15 minutes by continuously working out elaborate mnomonic schemes. When asked how he had been able to remember the number for so long, he replied "Its easy. You just remember the number 8. You see, 5, 8 & 4 add up to 17. You remember 8, subtract it from 17 and it leaves 9. Divide 9 in half & you get 5 & 4, & there you are 584: Easy." A minute or 2 later, HM was unable to recall either 584 or any of the associated complex train of thought. In fact, he did not know that he had been given a number to remember.

More general terms

• Homo sapiens

Additional terms

• hippocampus (hippocampal formation)
• memory
• Milner, Brenda