Remembering Breakthroughs

A New York Times profile earlier this week on Brenda A. Milner, Sc.D., credited her with changing “the course of brain science for good as a newly minted Ph.D. in the 1950s by identifying the specific brain organ that is crucial to memory formation.”

Milner

Photo credit: Owen Egan; Courtesy of the Montreal Neurological Institute, McGill University

Milner, a Dana Alliance for Brain Initiatives member, identified the hippocampus and other areas of the brain that process memory while working with Henry Molaison, more commonly known as H.M., who developed amnesia at age 29 from the removal of tissue from both his medial temporal lobes, a surgery that was supposed to alleviate his epilepsy.

With the help of H.M., Milner discovered that memory was processed in the medial temporal lobes, which was why he could no longer form new long-term memories. He was, however, able to learn new tasks, meaning he must remember the actions in another part of the brain. His ability to acquire new skills proved to Milner there are two types of memory that occur in different parts of the brain – explicit memory, which recalls describable details like facts and events, and implicit memory, for unconscious memories such as actions and procedures. Milner described this finding in a 2010 Dana Foundation interview:

I went to the McGill psychology department and borrowed learning tasks to give him [H.M]. I took down a maze task, which I was sure he wouldn’t learn, and he didn’t. It was a nice control test, because he showed absolutely no progress over three days. Then I gave him the mirror drawing task. H.M. did 30 trials over three days and at the end of the last trial, his performance was absolutely perfect. I can still remember him looking at what he had drawn, saying: “This is strange. I thought this would be difficult, but it looks as though I’ve done it rather well.” I was very excited because it showed that he could have this excellent performance without any awareness that the reason he was doing so well was that he had had the chance to practice the task over three days.

When I saw that H.M.  had this beautiful learning of something he had no memory of having acquired, I then speculated that this task, which involved motor learning, depended on a different system in the brain. His surgeon had damaged his medial temporal system, but this was a kind of learning that was unaffected by this operation, so therefore it must involve other structures.

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Summer Reading List: Brain Books

As someone who recently finished the latest Dan Brown book, I understand the entertainment value of a fluff read–particularly when on vacation. But as the Fourth approaches and many of you look forward to beach getaways or some down-time in the back yard, consider reading one of the brain-related books recently published by our Dana Alliance for Brain Initiatives (DABI) members. You’ll certainly learn something and your friends are sure to be impressed.

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H.M.’s brain: part of a good month for memory

As December began we reported
on the imminent sectioning of the brain of Henry Molaison, or H.M., whose inability
to form new memories has fascinated neuroscientists for decades. Many other
articles, both about H.M. specifically and memory more generally, have appeared
in the weeks since the sectioning.

Dana’s Brain
in the News
advisor, Guy McKhann, made H.M. the subject of his December
commentary
. McKhann provides a neuroscientist’s first-person perspective on
why the continuing study of Molaison’s brain is important.

In addition to the San
Diego Union-Tribune
article
we mentioned in our initial coverage, the Hartford
Courant
published an in-depth
piece
about Molaison on Nov. 29. On Dec. 4, after the sectioning had begun,
a public radio program in San Diego featured a conversation
with researcher Jacopo Annese of the University of California, San Diego (who
was in charge of the sectioning) and Dana Alliance member Suzanne Corkin of the
Massachusetts Institute of Technology (who studied Molaison extensively during
his life and wrote
briefly about him in a 2008 Cerebrum book review). CNN also posted a story
that day about Molaison.

Just this week, the New
York Times
published
a piece
that focuses less on Molaison and more on the dissection technique,
which resulted in about 2,500 paper-thin slices of the brain. The scientists in
charge plan to extend the process to many other donated brains, both normal and
abnormal, and put up digital reproductions of slices online for access by
researchers worldwide. This combination of precision and accessibility should
open new doors in the study of brain anatomy, the researchers say.

And what of memory in general? This past week, Canada’s National Post has run a series of
well-thought-out articles
that delve deeply into the subject, with a couple
of passing mentions of H.M. but a much broader approach; first on the list is “Is [Memory] What
Makes Us Human?”
A related podcast
features an interview with the author of the series, Joseph Brean.

-Dan Gordon

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