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Neuroplasticity is the capacity of the nervous system to modify its structure and function in response to experience, activity, injury, or environmental change. It encompasses processes at multiple scales — from molecular changes within individual synapses to large-scale cortical reorganisation — and operates throughout the lifespan, though its mechanisms and scope change with age.

A neurotransmitter is a chemical messenger used by neurons and other excitable cells. In the classical model, it is made by a neuron, released from the presynaptic terminal, crosses the synaptic cleft, and binds to receptors on a postsynaptic cell. This binding can excite the receiving cell, inhibit it, or modulate how it responds to other signals.