Plasticity in somatic sensory cortex refers to the ability of cells to change their response to sensory inputs. Typically changes depend upon activity-induced modifications of synaptic strength. Increasing or decreasing synaptic strength is orchestrated through changes in transmitter release from axon terminals, in glutamate receptor properties, in postsynaptic cell depolarization, and in calcium activation of a cascade of intracellular events. Synaptic changes in cortex are facilitated by the level of cortical excitability and modulatory transmitters that create the background for activity arriving over sensory pathways. Ongoing activity initiated by peripheral receptors creates the patterns of activity in cortex that map the activity-dependent representation of the body onto cortex.