Plasticity can be a blessing when the ongoing sensory input we receive is pleasurable, for it allows us to develop a brain that is better able to perceive and to savor pleasant sensations; but that same plasticity can be a curse when the sensory system that is receiving ongoing input is the pain system. That can happen when a person slips a disc, which then presses repeatedly on a nerve root in her spine. Her pain map for the area becomes hypersensitive, and she begins to feel pain not only when the disc hits the nerve when she moves the wrong way, but even when the disc is not pressing hard. The pain signal reverberates throughout her brain, so that pain persists even after its original stimulus has stopped

Plasticity can be a blessing when the ongoing sensory input we receive is pleasurable, for it allows us to develop a brain that is better able to perceive and to savor pleasant sensations; but that same plasticity can be a curse when the sensory system that is receiving ongoing input is the pain system. That can happen when a person slips a disc, which then presses repeatedly on a nerve root in her spine. Her pain map for the area becomes hypersensitive, and she begins to feel pain not only when the disc hits the nerve when she moves the wrong way, but even when the disc is not pressing hard. The pain signal reverberates throughout her brain, so that pain persists even after its original stimulus has stopped