Neuroplasticity

Neuroplasticity, also called neural or brain plasticity, describes how the nervous system keeps rewiring itself throughout life. Change happens at several scales: individual synapses grow stronger or weaker, new synapses form while unused ones are pruned away, dendrites sprout new branches, glial cells adjust, and in a few regions new neurons are added. Whole maps in the cortex can also be redrawn, so that one area takes over work once done by another.

Synaptic plasticity, a change in how strongly one neuron influences another, is the best-studied form. Short-term changes last fractions of a second, while long-term ones, such as long-term potentiation, can persist for hours to years and are the leading explanation of how memories are stored. The idea that active connections become stronger goes back to the psychologist Donald Hebb in 1949. Plasticity is greatest in childhood, when critical periods shape abilities such as vision and language, but adults keep a substantial capacity for change.

Neuroplasticity explains why practice improves a skill and why people often regain function after a stroke or brain injury, as rehabilitation trains surviving regions to take over lost tasks. It can also misfire: after an amputation, reorganization of the body map in the cortex can give rise to phantom limb sensations.