Human hippocampal activation during transitive inference.

The medial temporal lobe contains multiple structures whose mnemonic operations need further delineation. One model posits the function of the hippocampus as a relational binder, collaborating with overlying cortices that perform encoding and retrieval operations. For instance, lesions of the hippocampus leave intact the learning of paired-associates while impairing the ability to synthesize information across pairs. We test this relational model with two PET studies of normal humans during a transitive inference task using faces that either have or lack relationships across the stimulus pairs. Both studies converge to support a relational processing model of hippocampal function.