The term multiple memory systems describes the idea that there are several independent parallel systems of neural structures each of which is specialized to process and store a different kind of information. A major form of evidence for this idea is experimental dissociations of brain structures and memory types in humans and rats. In both species, damage to the medial temporal lobes (hippocampus and related structures) impairs declarative memory but leaves procedural (skill) memory and emotional memory (Pavlovian conditioning) intact. Damage to the basal ganglia (caudate nucleus) impairs only procedural memory, and damage to the amygdala impairs only emotional memory. Other evidence shows that the outputs of the systems interact to control behavior both cooperatively and competitively.