Described by James Papez in 1937, the Papez circuit of the brain is one of the major pathways of the limbic system and is chiefly involved in the cortical control of emotion. The Papez circuit plays a role in storing memory. Papez discovered the circuit after injecting rabies virus into a cat's hippocampus and monitoring its progression through the brain. The initial pathway was described as follows:
- Hippocampus → fornix → mammillary bodies
- Mammillary bodies → mammillothalamic tract → anterior thalamic nucleus
- Anterior thalamic nucleus → genu of the internal capsule → cingulate gyrus
- Cingulate gyrus → cingulum → parahippocampal gyrus
- Parahippocampal gyrus → entorhinal cortex → perforant pathway → hippocampus
Since then, new findings in neuroanatomy and brain function have elucidated a larger circuit that also includes the prefrontal cortex (PFC), amygdala, and septum among other areas. The PFC and amygdala are key components in this larger loop.