Fig. 1.

A) Schematic of the principal connections described by Papez (1937) that constitute a serial circuit for the experience of emotions. B) Updated schematic depicting major, direct interconnections between the sites in Papez circuit, based on axonal tracing data from the rat and nonhuman primate. The schematic also provides information on the pathways linking these structures. Blue arrows, fibres in mammillothalamic tract; green arrows, fibres in fornix; purple arrows, fibres in cingulum bundle; red arrows, fibres in internal capsule. (Note that the parahippocampal projections to the rat anterior thalamic nuclei join the internal capsule, while the corresponding projections in the macaque involve the fornix). Abbreviations: MTT, mammillothalamic tract.