Neural plasticity (neuroplasticity) refers to the brain's ability to change its structure and function in response to experience, learning, development, and injury. It operates at multiple levels: synaptic plasticity (strengthening or weakening of individual connections), structural plasticity (growth of new synapses and dendrites), and large-scale reorganization (remapping of cortical representations). Plasticity is the biological basis of all learning and memory and enables partial recovery from brain damage.
Forms of Plasticity
Experience-dependent plasticity reflects the brain's response to environmental input: musicians develop enlarged cortical representations for their practiced hand, London taxi drivers have larger hippocampi, and learning to juggle produces detectable gray matter changes within weeks. Experience-expectant plasticity occurs during critical periods when the brain requires specific input for normal development (e.g., visual input for visual cortex development). Compensatory plasticity enables recovery after brain damage by recruiting alternative neural pathways.
Plasticity is greatest during critical (or sensitive) periods in development — windows when the brain is especially responsive to environmental input. After critical periods close, plasticity is reduced but not eliminated. Recent research has identified molecular mechanisms that regulate critical period opening and closing (including perineuronal nets and specific neurotransmitter systems), raising the possibility of reopening critical periods to enable adult learning or recovery with the plasticity of the developing brain.