RIP Patient H.M.

Patient H.M. just died:

In 1953, he underwent an experimental brain operation in Hartford to correct a seizure disorder, only to emerge from it fundamentally and irreparably changed. He developed a syndrome neurologists call profound amnesia. He had lost the ability to form new memories.

For the next 55 years, each time he met a friend, each time he ate a meal, each time he walked in the woods, it was as if for the first time.

And for those five decades, he was recognized as the most important patient in the history of brain science. As a participant in hundreds of studies, he helped scientists understand the biology of learning, memory and physical dexterity, as well as the fragile nature of human identity.

On Tuesday evening at 5:05, Henry Gustav Molaison -- known worldwide only as H. M., to protect his privacy -- died of respiratory failure at a nursing home in Windsor Locks, Conn. His death was confirmed by Suzanne Corkin, a neuroscientist at the Massachusetts Institute of Technology, who had worked closely with him for decades. Henry Molaison was 82.

If you have ever been in an introductory neuroscience class, you have heard of Patient H.M.

To cure, his intractable epilepsy, he underwent a procedure during the 50s that removed much of his medial temporal lobes in his brain including critical structures to memory in the brain: the hippocampi. They did not know this at the time, but the hippocampi are critical to the formation of new memories. Hence, H.M. could remember things that happened prior to his procedure but could not form new episodic memories from that time forward. (If you have ever seen the movie Memento, Patient H.M. was a lot like that.)

I say episodic or declarative because we actually learned that H.M. could form new memories; they just could not be memories for events. For example, over several days they trained him to trace a star with a thin line by looking in a mirror. They discovered that over the training period he got better at the task. He could form new memories for procedures, just not for episodes. During this training period, the experimenters would have to repeatedly introduce themselves, even though he had known them for years.

Understanding what had been taken from H.M. allowed us to understand critical aspects of how the brain is structured. His case has probably been the most useful in the entire history of neuroscience.

R.I.P. Henry Molaison. Through understanding you, we came to understand ourselves. You lost memory, but you were the most memorable of us all.

Hat-tip: Kate