Friday, December 4, 2009

Remembering the Man Who Forgot

If you’ve ever taken an intro psychology class, you’ve probably heard of patient H.M. For years H.M. suffered from epileptic seizures. They got so bad that in the 1950s, he opted to undergo an experimental surgery. This surgery removed a portion of his brain, and the theory was that in doing so, would cure his epileptic seizures.

The surgery was a success, as far as the seizures were concerned, but his doctors were surprised by the “side effects” of the surgery. H.M. became an anterograde amnesiac. Basically, he lost the ability to create new long-term memories.

However, H.M. was able to turn this misfortune into an opportunity for others. Rather than fade into obscurity, H.M. opted to continue working with doctors and researchers. Through this 50 year collaboration came a wealth of information that advanced our understanding of the brain and memory formation, ultimately informing neuroscience research and shaping health care today.

Before H.M., it was thought that memory was a generalized process of the brain. His case provided scientist with the first evidence that contradicted this thought. If memories were generalized, the removal of a portion of the brain should not have obliterated memory formation. The fact that for H.M., the direct result of his surgery was the loss of long-term memory showed conclusively that memories were a function of specific brain regions.

Beyond this, doctors were now able to identify that there were also categories of memory. H.M. retained his procedural memory and short-term memory capabilities, but lost long-term memory formation.

For example, while H.M. could remember how to ride a bike (a memory referred to as a muscle memory because it involves an action of the muscles), he couldn't remember HOW he learned to ride a bike. His procedural memory was intact, and he had a decent short-term memory, but he couldn't convert those short-term memories to long-term. If you asked him what he had for breakfast two hours after he ate, he wouldn't be able to answer you, and beyond that, he wouldn't even remember eating breakfast!

What is most interesting about H.M.'s case is that although it was generally accepted that he could not form long-term memories, there were exceptions to the rule. For example, he remembered the assassination of John F. Kennedy, something that given his condition, he shouldn't have remembered.

We know that the brain can be adaptable. For example, a person who is blind generally develops a more keen sense of hearing, and this happens because the area responsible for vision adapts, becoming sensitive to detecting sound. This finding with H.M. has researchers wondering if the same phenomenon occurs with memories. Can other brain regions "fill in" for lost or damaged memory regions; or was his limited ability to form long-term memories present because there were some memory-associated brain tissue left behind from the surgery?

H.M. died December 2, 2008, but his contribution to science lives on. This man spent 50 years of his life working with scientists and researchers so that we can better understand the brain, and in doing so, helped advance the means by which we treat patients with for those with brain injuries, impairments, and other neurological disorders.

But his story doesn't end here. He donated his brain to science, giving researchers the ability to physically examine the structures of his brain. We can now relate the years of observational data that H.M. contributed to the actual physical structures of his brain. This donation could potentially undercover an entirely new level of understanding as to how the brain and memory formation works.

Often when we hear of breakthroughs in medical research, we tend to forget that there are real people behind these advances; people who selflessly donate their time and their bodies to help discover medications like Aspirin, Prozac (for mental health), and Lipitor (for cholesterol).

As a researcher, I'm constantly thinking about how research findings translate to medical miracles for our diverse human population. This is something that I've been focused on during my time at Research!America, and a topic that I will revisit in later posts.

For now, I'd like to take a moment to thank all of those people who have enrolled in clinical research trials, and to encourage others to learn about these trials. H.M. is one example of the difference that one person can make by volunteering for clinical research.

Visit us Tuesday to learn more about how H.M. is contributing to the field even after his death.

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