" The neuroplastic brain evolved in ambulatory beings who ranged around the world, always having to explore unknown territories. In other words, the brain evolved to learn. As people become immobile, they see less, hear less, and process less new information, and their brains begin to atrophy from the lack of stimulation (unless they are fundamentally thinkers, and even then the neuroplastic systems require physical movement to generate new cells and nerve growth factor). "

― Norman Doidge , The Brain's Way of Healing: Remarkable Discoveries and Recoveries from the Frontiers of Neuroplasticity