The impression a walnut leaves when it’s been pressed against and removed from a blob of Silly Putty is a copy of a walnut. Starting with one walnut, you end up with two: the walnut itself and the walnut-in-the-Silly Putty. The walnut, in a sense, has been duplicated. Of course, only one of the two walnuts is actually a walnut. The other one is a blob of Silly Putty indented where the walnut protrudes, concave where the walnut is convex, rubbery where the walnut is nutty. One is real and the other is fake. Likewise, a memory is a copy of something. And just as it’s impossible to make a copy of a document when the copier is empty of paper, it’s impossible to make a memory of a walnut without some substance to remember it, to reflect in its contours the contours of the walnut, to absorb on its surface the daylight the walnut scatters, to organize itself into an echo of a walnut.
Memories don’t exist apart from the substances that capture and hold them. A photograph of a sunset can’t be separated from the paper it’s been printed on. The photograph is the paper it’s been printed on. An impression of a walnut can’t be separated from the Silly Putty it’s been pressed against. The impression of the walnut is the Silly Putty it’s been pressed against. Memories don’t float freely through a vacuum. They’re anchored in some substance. Even when the substance isn’t obvious or when the substance is hidden from view, whenever a memory is made, somewhere there is a substance remembering it. Inside my phone, a chip holds memories of songs. I don’t know what it looks like, but I know it’s in there somewhere.
Every day, the contents of my laptop are automatically uploaded to a web server somewhere. In the event that my laptop is stolen or lost in a fire, in order to retrieve my files – copies of my files, actually, very precise copies of my files – all I have to do is request them from the server and download them to a new computer. The files live longer than the laptops I use to create them, each laptop serving as a temporary home for the files, a disposable shell. My files are backed up, as they say, in the clouds. Of course, the files aren’t literally in the clouds, but since the information is transmitted wirelessly to faraway computers hidden from my view and can be pulled from thin air at the touch of a button when I need it, it feels like the information is floating magically around me and clouds feels eerily appropriate.
Where are the contents of my laptop actually recorded? In a system of networked web servers dotting the surface of the earth. Servers are electronic appliances made of plastic and metal and semiconducting materials that store and transmit information to and from computers around the world. When you search the internet for a web page, for example, your request is sent to a nearby server where copies of millions of web pages are stored and organized for easy access. Although they’re invisible to us, servers are very busy, accounting for up to 2.5% of all energy consumed in the United States. Far from being in the clouds, my files are backed up in cold hard machinery. As long as the hardware survives and remembers the files, whenever my laptop dies, all I need to do is tap into the “clouds”, that web of remembering substances dotting the surface of the earth.
Brain, of course, is the ultimate remembering substance. Like web servers, they are also hidden from view and dot the surface of the earth in a network of wireless transmissions. As plastic as vinyl, as durable as film, and more magical than memory foam or Silly Putty, a brain is a living tape recorder recording memories of sounds, a living camera recording memories of daylight. It’s also, strangely enough, able to register and record things that are more elusive: thoughts and emotions and dreams, subtleties of touch and texture, how rosemary is sticky and prickly, how the smell of it makes you feel.
Each sensation presses itself into the wet substance of the brain where it lingers. Most of these moments are disposable snapshots – the way your face looks in the mirror in the morning, the sound of bran flakes in your mouth, the way sunlight piercing the skylight feels savored through closed eyelids. These memories linger on the film for a moment before being erased and forever forgotten. Those with emotional impact – a hauntingly beautiful moonrise, a surprising and horrifying accident – or those which through repetition have been seared into the substance of the brain – how a foot works car brakes, your name and where you are from – are transferred to more permanent storage and are more resistant to being erased.
A brain can’t press itself against a walnut directly like Silly Putty can. Silly Putty can press itself against a walnut, into its ridges and grooves, and when the walnut and the Silly Putty have separated, an impression of the walnut remains: the walnut lingers. This is the essence of memory. A walnut doesn’t leave a literal impression in the brain, but it does leave a mark there. How exactly does a brain remember what a walnut looks like or the way a walnut feels? How does a walnut leave an “impression” in the brain?
Imagine your eyes are closed. You are holding a shelled walnut in your hand. Since your brain cannot press itself directly against the curlicues of the walnut, it must command your hand to press the pads of your fingers against the curlicues of the walnut on its behalf. The way the walnut presses into the touch sensors of your fingertips forms a map of the walnut in your brain. Drop the walnut to the floor and the map of it – the copy of it – lingers in your brain. There are two walnuts: the walnut itself and the walnut-in-the-brain. This is the essence of memory.
A brain can’t see a clementine directly, so it sends forth a pair of eyeballs to collect on its behalf the daylight the clementine scatters. Like a camera that receives light through a hole and records a likeness of the clementine on film, the retina receives light through a hole – the pupil – and records a likeness of the clementine in the brain. Daylight types a message on the keypads of the retina. The retina sips orange and yellow light, tasting the colors of the clementine, etching this information into the tissues of the brain. The clementine leaves an impression in the brain; the brain does an impression of the clementine, registering a yellow-orange fruit-oval in the cinema of remembrance.
Now there are two clementines: the clementine itself and the clementine-in-the-brain. Of course, a brain does not record a literal version of a clementine – you won’t find a tart, squat, orange citrus fruit if you look into a brain, at least not from the outside looking in – but the brain does record some version of a clementine, some organized echo of a clementine, recognizable to the brain as a clementine through the use of labels and pictures it fashions. The brain becomes like a clementine.
Brain is a good remembering substance because it’s highly plastic, that is to say, highly shapeable. It’s continually reshaping itself into maps of the things it experiences with the assistance of its sensory organs and it does so with high fidelity. As amazing as it sounds, it’s true. A brain reshapes itself into precise maps of everything it experiences and remembers. Maps of sunsets, maps of clementines, maps of songs, maps of soups: all of these things press their impressions into the brain, leaving behind maps of themselves in the process like so many walnuts in Silly Putty. Impressively, the brain can even layer and intermingle these maps simultaneously, recalling, for example, that time you savored a clementine watching the setting sun in the middle of the Indian Ocean while a boy with a ukulele sang Yesterday. Take that, Silly Putty!
Brain is a living memory metal, reshaping itself to capture in the contortions of its tissues neurological echoes of its environment. Does this mean that, as the brain experiences things – the dishes in a seven-course meal, the fast-moving pictures in a movie – it continuously reshapes itself, echoing in real time the objects of its experience? Does this mean that as you ride a bicycle down the street, enjoying the sounds of the birds and the sights and the smells of the neighborhood, the brain is echoing these sensations as fast as your feet are pedaling? Yes, the brain is that responsive and that fluid. The connections of its neurons are so everchanging, in fact, some consider the brain to be liquid, an ever-churning clay, a mirror of molten glass, a miraculous remembering substance.