CNS 2014 Blog: Keynote Address by Suzanne Corkin
Let’s test your memory: What did you eat for dinner last night? That’s an easy answer. How about what’s the capital of Paris? For most, that’s easy as well. How about this one: How do the pedals work on a bike? That one may be tougher to answer.
Answering each of these questions uses a different memory circuit in the brain, as Suzanne Corkin of MIT explained in yesterday’s keynote address at the CNS meeting in Boston. We owe most of what we know about these different brain circuits to one man: Henry Molaison, widely known as H.M. After having parts of his brain removed in a 1953 operation to address his intractable epilepsy, H.M. was left with a unique type of amnesia. He then spent the next 55 years working with neuroscientists, including Corkin, to revolutionize human understanding of memory.
Many people, especially in the neuroscience community, have read about H.M. but few have heard his voice. In a captivating 6 minutes during Corkin’s talk, she played an interview with H.M. from 1992. We in the audience could hear firsthand the differences between his recollection of different types of memories and information. He could not remember what he had for lunch that day (“don’t know, to tell you the truth”) or who was U.S. President at the time (George W. Bush) but could remember many details of World War II, including when the U.S. got involved and who was President (FDR). He could not remember when or how he met Corkin but knew she was someone familiar.
Corkin detailed what scientists have learned about the types of memory that his operation affected. Because of the removal of his medial temporal lobe, he was essentially left without the ability to store long-term memories – able only to hold short-term memories (about 30 seconds). He no longer had any episodic memory capability, of events at specific times and places. He still had good non-declarative memory – things that we learn and demonstrate through performance, like the ability to ski. Such motor skills “endure for decades,” Corkin said, “hence the adage ‘you never forget how to ride your bike.’”
In a difficult task, in which participants cannot see their hand, pen or the image to trace, but instead see a mirror image, they must learn through practice how to trace the image. Although even challenging to healthy subjects, H.M. was able to perform well in this task.
There were other apparent anomalies in his memory abilities. For example, in 1966, he was asked to draw a floorplan of his 2-bedroom home. He was able to do so accurately, and when asked 11 years later to draw it again, even after having moved out a few years before, he was still able to accurately draw it.
Contrast the tracing task, though, with another visual task in which he was asked to draw an image he had been shown. He could do so immediately after seeing the image, but an hour later, he was stumped.There was also another type of memory not entirely impaired by H.M.’s amnesia: semantic memory. While he was unable to learn new vocabulary words, he was able to remember, for example, the names and some distinguishing details of certain celebrities.
Corkin described the many studies that have documented H.M.’s memory capabilities while he was alive and also described the rich information garnered from his generous donation of his brain after his death in 2008. The brain was donated to Massachusetts General Hospital, where it was imaged hours after his death. The brain flew “on Jet Blue,” Corkin said, to UC-San Diego, where it was cryogenically preserved and dissected into thousands of thin slices – with a stain applied to each slice as it was imaged.
She ended the talk by warmly recalling his pleasant personality. Calling H.M. gentle and funny, she told some stories of herself and others working with him. Once when a researcher locked his keys in the room and said he forgot them, H.M. replied: “at least you’ll remember where you put them.” And she recalls him saying once to another researcher to sum up his years of working with him: “It’s a funny thing, you live and learn. I’m living and you’re learning.”
-Lisa M.P. Munoz
Suzanne Corkin’s recent book The Permanent Present Tense: The Unforgettable Life of Amnesic Patient H.M., discusses the body of memory research learned from H.M.