People and animals learn to avoid pain provided that warning stimuli are available to signal pain-inducing events. Such learning is generally of two types, active and inhibitory. Active avoidance refers to movements learned in response to warning stimuli for the purpose of avoiding pain. Inhibitory avoidance refers to inaction, learned because action in the presence of the warning stimuli has previously led to pain.

Limbic and Motor Systems

Research implicates the brain's limbic and motor systems in the mediation of avoidance learning. The limbic system is a vast network of interconnected regions including the amygdala, hippocampus, limbic thalamus and the cingulate area of the cerebral cortex. Relevant parts of the motor system include the striatum and the nucleus accumbens. Many laboratory studies of the neural substrates of avoidance learning involve locomotion (or its inhibition). Therefore, areas of the brain concerned...