Forgetting is the horrible, beautiful necessity that keeps the past from swallowing the present but that, given too free a hand, picks apart the very strands of selfhood. As recently as a half century ago, since we didn’t understand memory we had no idea of how to account for its loss, until an irresponsible craze for lobotomizing patients produced a new wave of humans with hacked brains whose various degrees of amnesia pointed the way towards a new model of memory and its afflictions.
No case taught us as much as that of H.M., a man whose declarative memory was all but eliminated by an anti-epilepsy surgery when he was 27, and whose neural story was told over the span of five decades by MIT researcher Dr. Suzanne Corkin (1937-2016). She began her work with H.M. in 1962 and continued probing the intricacies of his mental world until his death in 2008, and in between shed vitally important nuance on our brain’s remarkable variety of memory mechanisms.
Prior to Corkin and H.M., there were numerous theories about how memory might work, dividing the various phenomena of mental storage into theoretical kingdoms that were difficult to prove or reject. Is episodic memory (memory about the succession of sights, sounds, and impressions that make up a moment in life) stored the same way as semantic memory (memory for facts and dates)? How does memory for the performance of a physical task (like soldering a circuit or juggling a ball) differ mentally from memory for people and places?
What was needed to start teasing apart the fibers of our capacity for information retrieval was a person with localized brain trauma whose memory could be tested to determine what parts of the brain were needed to remember different kinds of data. Unfortunately for humanity, but fortunately for the study of memory, the fad for lobotomies that swept America and Europe from the 1930s through 1950s provided just such people. The most infamous practitioner, Walter Freeman, could knock out dozens of lobotomy operations a day using an ice pick thrust under the eye socket.
I’ll give you a couple of moments to process that.
For all the initial recklessness of its application, controlled use of lobotomy procedures showed some hope as a cure for people suffering from extreme epilepsy. Patients, cut off from a normal life by the omnipresent threat of grand mal seizure, and suffering the side-effects of prolonged exposure to anti-seizure medication, grabbed at the lifeline of experimental brain surgery and some found relief there.
Henry Molaison did not. Submitting to surgery at the age of 27, both hippocampi and a large portion of his amygdala were removed in an attempt to cure his epilepsy. While the severity of that epilepsy did decrease, it came at a terrible cost. Henry was unable to form new memories. He was trapped within a thirty second span of available recall, a “permanent present tense” as Dr. Corkin described it in the title of her book detailing her decades of study of Molaison’s case.
Let’s stop and appreciate that for a moment. Think what it must be like to have no memory of what you did this morning, or five minutes ago, of seeing everybody around you always as strangers, of having no ability to plan for the future because you have no notion of what you’ve done. There is freedom there – freedom from the reliving of painful mistakes and loss, but also endless frustration, knowing that so much of you is lost to yourself. Henry Molaison, through that surgery, ceased being a promising and diligent skilled worker, and became H.M., neuroscience’s most famous case study.
The examination of his capacities fell to Suzanne Corkin, who had begun her studies at Montreal’s McGill University under memory specialist Brenda Milner, investigating the role that the sense of touch plays in forming memories. Over the next fifty years, Corkin’s studies of Molaison provided the crucial data to prove that the hippocampi are the areas of the brain responsible for the formation of episodic memory and that even episodes dating before the loss of the hippocampi can only be extracted as hazy outlines afterwards, while previously learned semantic memory stays largely intact. Further, she found that, though totally unable to recall newly learned information, H.M. did still exhibit certain unexpected abilities.
When asked to complete the names of famous people, he would sometimes come up with answers he ought not have known because they did not become famous until after his operation. Shown a picture of Billie Jean King, he wouldn’t be able to bring her name to mind, but asked to complete the name “Billie Jean” with any last name of his choice, he picked “King.” How was somebody with no ability to recall even the last two minutes of his life able to unconsciously complete a famous name he had no business knowing? He was also able to, for certain experiments, perform them better each time he did them, regardless of not remembering ever having done them before. Using fMRI techniques to examine the processes of his brain, and cleverly designed experiments to isolate and probe rigorously defined types of memory tasks, Corkin detailed what information is and is not consolidated by the hippocampus, providing thereby a new appreciation of the realm of non-declarative memory and the richness of our cortex’s ability to create its own forms of recall in the form of working memory, face perception, and task familiarity.
Though Corkin is primarily known through her studies of H.M., analysis of his abilities made up only about 22% of her lab’s output at MIT. The rest included equally vital if less narratively dramatic work that sought to define precisely how Parkinson’s and Huntington’s disease, which attack different sections of the brain’s striatum, impair sequence and motor learning, thereby unveiling the striatum’s precise role in the creation of forms of non-declarative memory. She also sought insight into the neurochemistry of aging by harnessing the newest imaging methods to document changes in white matter over the course of growing older, and how those have various impacts on the subject’s ability to retrieve episodic, semantic, and task-centered memories.
Like her mentor, Brenda Milner, who was still actively involved in research into her nineties, Corkin continued her researches well into her seventies, when liver cancer finally claimed her at the age of 79 on May 27, 2016. She thought of herself and Henry Molaison as partners in a great project to open before the world at last the physical mysteries of memory, and from their work together there have sprung thousands of researchers and tens of thousands of papers which have mapped the persistence, fragility, and most importantly, variety, of our strategies for storing the past.
Hers was a very fine brain indeed.
FURTHER READING: Permanent Present Tense (2013) is Corkin’s history not only of her time studying H.M., but also of the development of memory science from its early theoretical days right through to the modern age of 7 Tesla brain imaging technology, and contains more twists and turns of the sneakiness of information storage and retrieval than I could have ever included here. Just when you think you’ve got figured out what Henry should and shouldn’t be able to do, she develops a new test which reveals unexpected abilities that themselves call for a new complexification of our sense of what stores what in the brain, and riding that roller coaster is a unique experience you should treat yourself to.