#livewired

As activity passes through the brain, it changes the structure. From the point of view of the vast forest of neurons in your skull, the organisational problem is tremendous: the nervous system must physically change itself to optimally reflect the world in which it's embedded. The individual changes must each make the right contribution to the network to embody the new knowledge, and the changes must be positioned to make a difference to behaviour when the right moment arises, some time in the future. A simplifying error when thinking about memory has been to assume that it is underpinned by a single mechanism of change. The classical story of strengthening and weakening synapses has brought us a long way, and artificial neural networks employing those principles can perform impressive engineering feats. But memory is more than dialling synapses in a large connection diagram. As we saw, simple synaptic models quickly lose the capacity to represent old data as new data stream in. The way memories degrade— with older memories having more stability — reveals the secret of different timescales of change. The synaptic model would be convenient for neuroscientists and Al engineers, but it's almost certainly not natures approach. Instead, the changes underlying memory are distributed widely over titanic. numbers of neurons, synapses, molecules, and genes. By analogy, just consider how the desert remembers the wind: it does so in the slope of its sand dunes, in the shape of its rocks, and in the evolutionary pressures that carve the wings of its insects and the leaves of its plants.

Just read your short story about the pirates and the mermaid. Where could I find more such writing? It's rare for a random short story on tumblr to grab my attention like that.

"Brain plasticity" (also called neuroplasticity) is the term we use in neuroscience. But I'll use that term only sparingly in this book, because it sometimes risks missing the target. Whether intentionally or not, "plasticity" suggests that the key idea is to mold something once and keep it that way forever: to shape the plastic toy and never change it again. But that's not what the brain does. It carries on remolding itself throughout your life. […] […] We spend our lives blossoming toward something, even as the target moves. Consider the feeling of stumbling on a diary entry that you wrote many years ago. It represents the thinking, opinions, and viewpoint of someone who was a bit different from who you are now, and that previous person can sometimes border on the unrecognisable. Despite having the same name and the same early history, in the years between inscription and interpretation the narrator has altered.

And this leads to a wild — but logically sound — speculation: Are parts of the world invisible to us that should be obvious? Imagine there were something like a cosmic rain that had existed your entire life. It would be completely invisible to you. Having never seen otherwise, your industrious visual system would have set the downward motion as its zero point. If the cosmic rain suddenly stopped, it would seem as though the whole world were suddenly moving upward. We would believe that something had just appeared — ascending rain-even though the real rain had just ended. And this situation could happen in any sensory channel: Imagine the beep-beep-beep of a cosmic alarm clock with no snooze button. All the time, all throughout the cosmos: beep-beep-beep. If it were totally regular, you wouldn't hear it at all, because your brain would have adapted to it. If the cosmic alarm clock suddenly ceased, everyone would suddenly hear a great beep-beep-beep, but we would have no idea that we were experiencing the aftereffect, with the "external" sound totally inside our heads? Successful adaptation makes regularities invisible.

One of the unsolved mysteries in neuroscience is why brains dream. What are these bizarre nighttime hallucinations about? Do they have meaning? Or are they simply random neural activity in search of a coherent narrative? And why are dreams so richly visual, igniting the occipital cortex every night into a conflagration of activity? Consider the following: In the chronic and unforgiving competition for brain real estate, the visual system has a unique problem to deal with. Because of the rotation of the planet, it is cast into darkness for an average of twelve hours every cycle. (This refers to 99.9999 percent of our species' evolutionary history, not to the current, electricity-blessed times.) We've already seen that sensory deprivation triggers neighbouring territories to take over. So how does the visual system deal with this unfair disadvantage? By keeping the occipital cortex active during the night. We suggest that dreaming exists to keep the visual cortex from being taken over by neighbouring areas. After all, the rotation of the planet does not affect anything about your ability to touch, hear, taste, or smell; only vision suffers in the dark. As a result, the visual cortex finds itself in danger every night of a takeover by the other senses. And given the startling rapidity with which changes in territory can happen (remember the forty to sixty minutes we just saw), the threat is formidable. Dreams are the means by which the visual cortex prevents takeover.

We generally go through life thinking there's me and there's the world. But as we've seen in this book, who you are emerges from everything you've interacted with: your environment, all of your experiences, your friends, your enemies, your culture, your belief system, your era — all of it. Although we value statements such as "he's his own man" or "she's an independent thinker," there is in fact no way to separate yourself from the rich context in which you're embedded. There is no you without the external. Your beliefs and dogmas and aspirations are shaped by it, inside and out, like a sculpture from a block of marble. Thanks to livewiring, each of us is the world.

Instead of encoding pixels or transcripts, we encode new stimuli with respect to other things we have learned, including concepts both physical and social. What we learn is represented in terms of what we already know. Two people can look at a list of important dates in Mongolian history, but if one of them commands a richly developed model of Mongolia, the new facts are more readily incorporated into her network of knowledge. For the other, who knows little about the country and has never been there, the facts have little scaffolding upon which to attach. Recall that in the pace layers model, slow layers provide a framework for the fast layers. As a result, early experience becomes foundational. It develops into the architecture upon which everything subsequent is built. Everything new is understood through the filter of the old. For better or worse, this makes some dreams of the future impossible. In the movie The Matrix, Neo and Trinity come across a B-212 helicopter on the top of a building. Neo asks, "Can you fly that helicopter?" Trinity replies, "Not yet, rings her colleague, and asks for "a pilot program for a B-212 helicopter." Her colleague frenetically hits keys on a collection of computers, and within a few seconds the program is uploaded into Trinity's brain. Neo and Trinity board the helicopter, and she expertly steers it between buildings. We would all love this future, but it's not going to happen. Why not? Because memory is a function of everything that has come before it. One person's knowledge of flying a B-212 helicopter might be encoded by its similarity to riding a motorcycle. Another person might have grown up on horses, so she builds the piloting knowledge on top of motor memories of steering a steed. A third person stores the knowledge in the context of a childhood video game. Each person grasps the task differently, making it impossible to have a standard set of instructions that is uploadable to any brain. In other words, unlike a computer, the "instructions" for flying the machine aren't a file; they are instead tied to everything that has come before in your life. Earlier experiences build an internal city of memory, into which each new resident must find his unique fit.