The brain is the organ that learns, so it is designed to be changed by your experiences. It still amazes me but it’s true: Whatever we repeatedly sense and feel and want and think is slowly but surely sculpting neural structure. As you read this, in the five cups of tofu-like tissue inside your head, nested amidst a trillion support cells, 80-100 billion neurons are signaling each other in a network with about half a quadrillion connections called synapses. All this incredibly fast, complex, and dynamic neural activity is continually changing your brain. Active synapses become more sensitive, new synapses start growing within minutes, busy regions get more blood since they need more oxygen and glucose to do their work, and genes inside neurons turn on or off. Meanwhile, less active connections wither away in a process sometimes called neural Darwinism: the survival of the busiest. All mental activity—sights and sounds, thoughts and feelings, conscious and unconscious processes—is based on underlying neural activity. Much mental and therefore neural activity flows through the brain like ripples on a river, with no lasting effects on its channel. But intense, prolonged, or repeated mental/neural activity—especially if it is conscious—will leave an enduring imprint in neural structure, like a surging current reshaping a riverbed. In the saying in neuroscience: Neurons that fire together, wire together. Mental states become neural traits. Day after day, your mind is building your brain. This is what scientists call “experience-dependent neuroplasticity,” which is a hot area of research these days. For example, London taxi drivers memorizing the city’s spaghetti snarl of streets have thickened neural layers in their hippocampus, the region that helps make visual-spatial memories; like building a muscle, these drivers worked a part of their brain and grew new tissue there. Moving from the cab to the cushion, mindfulness meditators have increased gray matter—which means a thicker cortex—in three key regions: prefrontal areas behind the forehead that control attention; the insula, which we use for tuning into ourselves and others; and the hippocampus. Your experiences don’t just grow new synapses, remarkable as that is by itself, but also somehow reach down into your genes—into little strips of atoms in the twisted molecules of DNA inside the nuclei of neurons – and change how they operate. For instance, if you routinely practice relaxation, it will increase the activity of genes that calm down stress reactions, making you more resilient.
-- Rick Hanson for The Greater Good Science Center at the University of California, Berkeley: How to grow the good in your brain
