On the other hand, numbers. I know people who can remember what their phone number was in houses they haven't lived in for thirty years. I'm lucky when I can remember what my phone number is now. In this day of passwords, PINs, and so on, there are a variety of number/letter combinations I'm expected to remember, and the maximum amount of these I seem to be able to recall is: one. For all of the passwords where this is possible, I use the same one. If anyone ever discovers it, I'm fucked. Fortunately, it's pretty obscure, so I don't think it's likely (meaning you shouldn't waste your time trying to figure it out).
It does, however, point up something odd about memory, which is how compartmentalized it is. People can be exceptionally good at certain types of memory, and rather bad at others. A few things, however, seem common to all sorts of memory; repetition improves retention, memory consolidation increases after sleep, and we all get worse at it (all types) as we age.
[Image licensed under the Creative Commons Michel Royon Ce message en français, Brain memory, CC0 1.0]
This last one is the subject of some cool research published in Nature, in a paper entitled "Increased NR2A:NR2B Ratio Compresses Long-Term Depression Range and Constrains Long-Term Memory," by Zhenzhong Cui, Ruiben Feng, Stephanie Jacobs, Yanhong Duan, Huimin Wang, Xiaohua Cao, and Joe Z. Tsien, as a collaborative project between Georgia Health Sciences University and East China Normal University. The experiments involved using transgenic mice that overproduced a neurotransmitter receptor called NR2A, and found that they were significantly poorer than normal at forming new long-term memories than ordinary mice were. The reason, the researchers speculate, is that this receptor is involved in weakening the synaptic firing patterns from old memories.
Put another way, it seems like one of the reasons we become more forgetful as we age is that we aren't as good at getting rid of things we already have stored in there. In an interview with the New York Times, study lead author Joe Z. Tsien compares our brains when young to a blank page, and older brains to a page from a newspaper. "The difference is not how dark the pen is," he said, "but that the newspaper already has writing on it."
"What our study suggests," Tsien added, "is that it’s not just the strengthening of connections, but the weakening of the other sets of connections that creates a holistic pattern of synaptic connectivity that is important for long-term memory formation."
In other words, our brains really do fill up and (in some sense) run out of space.
It's a funny thought, isn't it? One of the reasons I can't remember where I left my keys is because my brain still is determined to hang onto the name of my 7th grade English teacher (Mrs. Trowbridge).
I find this a fascinating result, partly because it contradicts my long-held belief (admittedly based on no evidence whatsoever) that no one ever gets close to the actual memory storage capacity of the brain. Also, it brings up the questionably prudent possibility of developing technology to selectively erase memories, the ethical and personal problems of which are memorably delineated in the wonderful movie Eternal Sunshine of the Spotless Mind. Not, in this case, to eliminate traumatic or unpleasant memories, as it was for Jim Carrey's character -- but to free up hard drive space.
Which, aside from the scary aspects, creates some interesting possibilities. Imagine reading your favorite book, seeing your favorite movie, hearing your favorite song again for the first time. Wouldn't it be cool to recapture the wonder of having a new experience over and over again?
In any case, this is only the beginning. A dear friend of mine, the brilliant (now retired) Cornell human genetics professor Dr. Rita Calvo, once made the prediction that "if the 20th century was the century of the gene, the 21st will be the century of the brain." We are, she said, right now with respect to our understanding of the brain approximately where we were in 1919 with respect to our understanding of genetics -- we know a little bit of the "what" and the "how much," but almost nothing about the "how" and the "why."
If so, we should be looking forward to some amazing advances over the next few years, and I'm sure I'll have to do a lot of reading to keep up with the research even well enough to teach competently my Introductory Neuroscience class. It's exciting, however, to think that we may finally be elucidating the inner workings of our most intricate organ, and finding out how it does one of the most mysterious things of all -- storing, and retrieving, information.
This week's Skeptophilia book recommendation is a brilliant look at two opposing worldviews; Charles Mann's The Wizard and the Prophet. Mann sees today's ecologists, environmental scientists, and even your average concerned citizens as falling into two broad classes -- wizards (who think that whatever ecological problems we face, human ingenuity will prevail over them) and prophets (who think that our present course is unsustainable, and if we don't change our ways we're doomed).
Mann looks at a representative member from each of the camps. He selected Norman Borlaug, Nobel laureate and driving force behind the Green Revolution, to be the front man for the Wizards, and William Vogt, who was a strong voice for population control and conversation, as his prototypical Prophet. He takes a close and personal look at each of their lives, and along the way outlines the thorny problems that gave rise to this disagreement -- problems we're going to have to solve regardless which worldview is correct.
[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]