Imagination

Pascual-Leone had profound observations about how neuroplasticity, which promotes change, can also lead to rigidity and repetition in the brain, and these insights help solve this paradox: if our brains are so plastic and changeable, why do we so often get stuck in rigid repetition? The answer lies in understanding, first, how remarkably plastic the brain is.

Plasticina, he tells me, is the musical Spanish word for "plasticity," and it captures something the English word does not. Plasticina, in Spanish, is also the word for "Play-Doh" or "plasticine" and describes a substance that is fundamentally impressionable. For him our brains are so plastic that even when we do the same behavior day after day, the neuronal connections responsible are slightly different each time because of what we have done in the intervening time.

"I imagine," Pascual-Leone says, "that the brain activity is like Play-Doh one is playing with all the time." Everything that we do shapes this chunk of Play-Doh. But, he adds, "if you start out with a package of Play-Doh that is a square, and you then make a ball of it, it is possible to get back to a square. But it won't be the same square as you had to begin with." Outcomes that appear similar are not identical. The molecules in the new square are arranged differently than the old one. In other words, similar behaviors, performed at different times, use different circuits. For him, even when a patient with a neurological or psychological problem is "cured," that cure never returns the patient's brain to its preexisting state.

"The system is plastic, not elastic," Pascual-Leone says in a booming voice. An elastic band can be stretched, but it always reverts to its former shape, and the molecules are not rearranged in the process. The plastic brain is perpetually altered by every encounter, every interaction.

So the question becomes, if the brain is so easily altered, how are we protected from endless change? Indeed, if the brain is like Play-Doh, how is it that we remain ourselves? Our genes help gives us consistency, up to a point, and so does repetition.

Pascual-Leone explains this with a metaphor. The plastic brain is like a snowy hill in winter. Aspects of that hill - the slope, the rocks, the consistency of the snow - are, like our genes, a given. When we slide down on a sled, we can steer it and will end up at the bottom of the hill by following a path determined both by how we steer and the characteristics of the hill. Where exactly we will end up is hard to predict because there are so many factors at play.

"But," Pascual-Leone says, "what will definitely happen the second time you take the slope down is that you will more likely than not find yourself somewhere or another that is related to the path you took the first time. It won't be exactly that path, but it will be closer to that one than any other. And if you spend your entire afternoon sledding down, walking up, sledding down, at the end you will have some paths that have been used a lot, some that have been used very little... and there will be tracks that you have created, and it is very difficult now to get out of those tracks. And those tracks are not genetically determined anymore."

The mental "tracks" that get laid down can lead to habits, good or bad. If we develop poor posture, it becomes hard to correct. If we develop good habits, they too become solidified. Is it possible, once "tracks" or neutral pathways have been laid down, to get out of those paths and onto different ones? Yes, according to Pascual-Leone, but it is difficult because, once we have created these tracks, they become "really speedy" and very efficient at guiding the sled down the hill. To take a different path becomes increasingly difficult. A roadblock of some kind is necessary to help us change direction.

... The Brain That Changes Itself, Norman Doidge