The capacity to replace old neuronal connections with new ones is referred to as neuronal plasticity. The Tibetan term for this capacity is le su rung wa (Tib. ལས་སུ་རུང་བ།, Wyl. las su rung ba) which may be roughly translated into English as "pliability." What it boils down to is that on a strictly cellular level, repeated experience can change the way the brain works. This is the why behind the how of the Buddhist teachings that deal with eliminating mental habits conducive to unhappiness.
- *Mingyur Rinpoche, The Joy of Living.