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permanent present tense

6 october 2013

A great deal of what scientists know – indeed, of what everybody sort of knows – about the human brain comes from study of just one human's brain, a research subject called, in the literature, simply "H.M." As with so many things medical, that knowledge was generated by observing what H.M. couldn't do, and his deficits were among the most profound and precise ever studied.

Until he died in 2008, though, H.M. remained just a pair of initials, the better to keep him from curiosity-seekers. Though he wouldn't have remembered such paparazzi ten minutes after he'd been sought out, his caretakers thought that making a celebrity of Henry Molaison would have compromised his dignity, and they were certainly right.

Experimental brain surgery in 1953 left Molaison unable to form new memories. (Suzanne Corkin, who led research on his condition, always calls him Henry, so I suppose I will too.) Amnesia in one of its purest forms, but amnesia isn't the simple thing of popular fiction and film, where you can't remember your name or how you came to wake up beside that dead policeman.

Henry Molaison's amnesia consisted of not being able to form new episodic or declarative memories. He could not tell you what had happened in his life since 1953, and he recalled little enough from before 1953 in any kind of vivid way. Yet he remembered many facts, words, and events from before his operation in a "semantic" sense, filed away in portions of his brain unaffected by the surgery. And he continued to form new memories of several important kinds: nondeclarative procedures (saliently, how to use a walker in his old age); "muscle memory"; habituation to changing circumstances; familiarity with people, animals, living quarters, and even some facts about the world; and associations based on "priming": so if someone said "John F.," he might well say "Kennedy," even though the 35th President became famous long after Henry's operation.

The general pattern of being unable to remember what you had for breakfast but clear on what your sixth birthday cake looked like is familiar to us from any elderly relative with Alzheimer's. But the contours of Henry's amnesia extended far beyond this simple dynamic. He was only 26 when his surgery (undertaken to control epileptic seizures) produced his condition. He continued to live an alert, social, and intellectually engaged life for many decades; until extreme old age, he was not demented. He just couldn't remember anything. He knew he couldn't remember anything, but his forgetfulness was so profound that he was for the most part well-enough adjusted: if you can't remember what yesterday was like, you can't get bored with today, or fearful about a sequence of identical tomorrows.

Suzanne Corkin (and a host of collaborators) learned in elaborate detail, over more than 40 years, exactly what Henry's brain could and couldn't process. As she gives crystal-clear exposition of her findings in Permanent Present Tense, we can't stop thinking about what's going on in our own brains as we read. If there ever was a book that impelled one to immediate meta-introspection, it's this one. Corkin presents a heap of material, and you start to worry about how well you're retaining it from one chapter to the next.

A lot of the models of memory that flourished in the early computer era were based on a vision of the brain as something like a large database. We store stuff, we access it, we articulate what we've accessed. This model is helpful, and often seems to illustrate things that Henry and other prime amnesic cases could and couldn't do. But it's equally true that memory is dynamic, even creative. Corkin addresses this side of memory, as well. If you can remember that sixth-birthday cake, it's because you've continually retrieved that memory over the years and retouched it; in pulling it out again, you're not recopying a text so much as rewriting one.

Henry's inability to store, retrieve, articulate – much less retouch – new memories is remarkable, if explicable when one realizes that his doctors removed parts of the brain that no-one would now remove (partly because "H.M." is now so famous a case). But the persistence and resilience of the brain is even more remarkable. One of the strangest moments in Permanent Present Tense comes when someone in the 1970s asks the long-amnesic Henry who's the main character in All in the Family (253). "Archie Bunker," says Henry without hesitation. And what does he call his son-in-law? "Meathead." This is a man, remember, who can't recall the names of his neighbors or his nurses. But he watches a lot of TV, and remembering TV shows, with their low-level ubiquity, is not like consciously remembering the name of that person who checks in on you once a week. Not just in degree but in kind: such "familiarities" are processed somewhere else in the brain, though they resemble declarative memories, and are indistinguishable from them unless you're an utter amnesic studied by neuroscientists from MIT.

Henry was anosmic as well as amnesic. I find this fascinating because I am hyposmic, though my memory, like most people's, is good for some things and lousy for others. We are often told that there is a deep link between memory and the sense of smell. Upon introspection, I don't find that to be true, though of course, tell that to Marcel Proust. Corkin's research doesn't establish any privileged link between smell and memory, though Henry lacked both – and that makes sense when you think about it. Sight, touch, and hearing, extraordinarily important senses for us primates, also have Proustian connections to memory.

Hearing in particular, and here is an under-examined feature of Henry's brain. Perhaps unfortunately for neuroscientific research, Henry was a relatively high-verbal, socially adept, and fairly handy kind of guy; but he seems to have been unmusical. Memory for melodies and song lyrics seems largely independent of declarative memory; there have been documented cases of amnesics as profound as Henry who nonetheless retained extraordinary abilities to perform, even to improvise, musical performance. At least as Corkin portrays it, we know little about Henry's ability to sing the Hit Parade of 1942 – or more intriguingly, the Top 40 of 1968.

Above all, Corkin stresses Henry's humanity. She has published innumerable papers that quantify Henry's cognitive abilities, and innumerable more remain to be published on Henry's brain, which has been frozen in gelatin somewhere in California and will someday be published, slice by slice, on the Internet. But as a subject only slightly more personalized than a maze-running rat, Henry has heretofore lacked a biography. Permanent Present Tense, for all its expository minutiae, is just such a humanist biography. We see Henry as he was before his operation, a kind of Popular-Mechanics, geeky guy with a treasured gun collection, shy around women (as an epileptic might be) but high-verbal and possessed of a rueful sense of humor. And then we see him as a lifelong amnesic, still funny and amiable, but sometimes depressed, sometimes unable to deal with others' inability to deal with him. We see him reading the same gun magazines over and over, solving crossword puzzles with expert proficiency, but learning no new vocabulary. (As a personal sidelight, I'd have liked to see Henry tested on knowledge-based "American" puzzles – as he frequently was – against wordplay-based "British" puzzles, which I myself prefer: I wonder if he'd have done even better on the British style.) We see him as asexual, but as the cynosure of attention from both sexes, a unique human being who attracted attention for what he showed us about humanity. We see him as a dog person. I think dogs (and even more so, cats!) are sometimes the measure of ourselves. I like that animals liked Henry Molaison.

Corkin, Suzanne. Permanent Present Tense: The unforgettable life of the amnesic patient, H.M. New York: Basic [Perseus], 2013.