How brain plasticity can lead to bad habits- and how to fix them

In his book, The Brain that Changes Itself: Stories of Personal Triumph from the Frontiers of Brain Science, Norman Doige poses the following question: if our brain is so plastic and malleable, why do we so often become prisoners of rigid and repetitive behaviors? In order to answer the question, he quotes a metaphor frequently used by Harvard professor Alvaro Pascual-Leone.

According to Dr. Pascual-Leone, the plastic brain is like a snow mountain in winter. Some aspects of the mountain, like its steepness, its rocks, the snow hardness, are relatively fixed and determine possible paths a skier might take on his way down. These relatively unchangeable mountain characteristics are like our genes, which determine particular aspects of our brain function.
When we ski down the mountain, we can control the snowblades and will end up at a spot on the mountain foot which is determined by the way we control the snowblades and also by the mountain characteristics. If you go down the mountain again, you will probably follow a path that is not exactly the same, but it will be similar. Should you spend all night skiing down the mountain, you would end up with a few paths that would have been followed many times, and others that would have been hardly used... and there would be paths created by you, and it would be very hard to avoid these. And these paths would no longer be genetically determined.

The mental "paths" that we create can lead to habits, both good and bad. If we develop a bad posture, it will be hard to correct it. If we develop good habits, they will also solidify.
Will it be possible, once these "paths" are established in our neural circuits, to leave them and choose alternative ones? Yes, answers Dr. Pascual-Leone, but it is not easy because, once created, these paths become very "fast" and efficient in guiding the skier down the mountain. Taking a different path is increasingly more difficult. We need some kind of "roadblock" to be able to change direction.

The "roadblock" concept has been therapeutically used, for example, in constraint therapy for rehabilitation of stroke patients: the hemiplegic patient tends to always use the healthy side of the body (the more efficient "path"). In order to avoid this, the physical therapist immobilizes the healthy limb, thus forcing the patient to take the more difficult and less efficient "path" (the paretic limb).

The same principle applies to many neuropsychological and educational instances (the Berlitz language learning method, for example, forces the student to use the target language- the more difficult "path"- when it blocks the efficiency of the student's native language - the easiest "path"- in an environment of total language immersion.