The principal connections of the hippocampus. Afferent connections (red arrows) from the cingulate gyrus (cortical association fibers) and amygdala converge on the entorhinal cortex (part of the parahippocampal gyrus) and connect with the hippocampus via a polysynaptic circuit (black arrows) from dentate to CA3, CA1, and subiculum neurons with output back to the entorhinal cortex. Efferent connections (broken arrows) are principally via the fornix to the anterior nucleus of the thalamus, septal nucleus, and mammillary body.