( A lot of this is lifted/inspired by “Remember This,” Joshua Foer, National Geographic, November 2007)
There is a woman known in medical literature as “AJ.” She remembers almost every day in her life since she was eleven. There is also a man known as “EP,” who remembers only his most recent thought. “My memory flows like a movie –nonstop and incontrollable” – says AJ. Her “inexhaustible memory for autobiographical details is so unprecedented and poorly understood” new medical term had to be coined for it: hyperthymestic syndrome. EP’s memory loss was caused by the herpes simplex virus, which left two walnut size holes in his medial temporal lobes.
There is one medial temporal lobe on each side of the brain. This space includes the hippocampus and several other regions responsible for turning our perceptions into long-term memories. The memories are not actually stored in the hippocampus, they are located an outer layer called the neocortex, but the hippocampus is what makes them stick. EP’s hippocampus was destroyed, which means that he can perceive things, but not store them. My brain works a little differently. I perceive things and also store them, but this stored information is mixed with invented things from my subconscious. I am sure this happens with other people as well, but I believe in my brain they are more pronounced.
There are two types of amnesia:
Anterograde - which means you can’t form new memories.
Retrograde – which means you can’t store old memories either.
Most of us exist in a nebulous realm in between the two. That three pound or so of wrinkled flesh attached to our spines is a weird goddamn thing. You remember useless TV trivia but can’t remember where you put your keys. What is memory? The best neuroscientists have been able to come up with is that “memory is a stored pattern of connections between neurons in the brain.” Real poetic isn’t it? There are about a hundred billion neurons, each making maybe 5,000 – 10,000 synaptic connections with the other neurons, which makes about five hundred trillion to a thousand trillion synapses in the average adult brain. You got all that? Here’s more. Synapses are strengthened, weakened, or formed anew constantly, even when we sleep. The very physical substance of us is always changing. Do you have a headache yet? Me too.
Damaged memory can profoundly affect your sense of time. EP has both kinds of amnesia. He does not remember he has a memory problem. He forgets that he forgets which makes every causal slip just an annoyance. He has no real sense of time, trapped in an eternal present. He is a happy all the time presumably because there is nothing in his life that can cause him stress. With my own memory affected, I am often struck with the perception that time is flowing way too fast around me. I am aware this is also something that everyone feels from time to time. But with me its effects past events as well – I can remember details from events in my life but not precisely when they happened. I go to bed some nights and wake up some mornings feeling as if several days have passed without my knowledge. That the memory of them is a blurry illusion my brain has cooked up for itself.
You can also learn things unconsciously without knowing you are learning them. This is because there are two kinds of memory- declarative and non-declarative – sometimes referred to as explicit and implicit. Declarative memory is things you actually remember, like what you ate for breakfast this morning. Non-declarative memory is things you know without consciously thinking about them, like knowing how to ride a bike. Those memories don’t rely on the hippocampus to be put together and stored, they occur in completely different parts of the brain. Motor skills are learned in the cerebellum, at the base of the brain, perceptual skills in the neocortex, habit learning in the brain’s center.
Most of the metaphors we use to describe memory suggest mechanical accuracy, but memory doesn’t really work that way. If you were to use an electrical probe to touch parts of the temporal lobe in a person, that person would describe vivid experiences that would resemble recollections, but they are actually closer to fantasies or hallucinations than to memories.
AJ’s memory would seem to embody the sort humans have idealized since ancient times. But your memories exist the way they do to protect you. Remembering everything is maddening and lonely for AJ. Like the Jorge Luis Borges story, if you remember everything, it becomes difficult to distinguish between the important and the trivial. You remember good things and bad things with equal clarity. Our modern technology has been quickly replacing our internal memories with external ones, and in the process something has been lost. The whole point of our brains and by extension our whole nervous system is to absorb present information and apply it to future events so we can react to it in the best possible way. Memory is our brain as a prediction machine, and a consistently crappy one at that.
EP takes the same walk virtually every day; he meets the same neighbors but reacts as if meeting for the same time. He responds to them in a friendly way because he’s learned through habit that these are people he should feel comfortable around. In other words, an unconscious learned feeling of comfort can trump your memory. I find this comforting. I have emotional connections to memories I am not sure actually happened. Many of these “memories” influence fundamental ways in which I interact with the world around me. In this way my emotional connection trumps my desire to know the objective truth about these events, particularly because some are virtually impossible to trace. They have become defining characteristics of who I am as a person.