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How does the entorhinal cortex connect the hippocampus to other brain regions?

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Patient H.M. and short-term memory loss explained — hippocampus Learn about Henry Molaison (better known as “patient H.M.”), whose short-term memory loss following a lobotomy helped researchers to understand how brain structures are related to brain function.

The entorhinal cortex serves as the primary gateway for communication between the hippocampus and the rest of the brain, facilitating both incoming and outgoing information. Located beneath the anterior region of the hippocampus, it connects to the hippocampal formation through two main neural circuits:1

Trisynaptic circuit: This pathway forwards information from the entorhinal cortex to the dentate gyrus via the perforant path. From there, signals travel to the CA3 region and then to CA1, eventually projecting back to the subiculum and the entorhinal cortex.1
Monosynaptic circuit: This direct pathway bypasses the dentate gyrus and CA3, transmitting information straight from the entorhinal cortex to the CA1 region.1

Additionally, the hippocampus exhibits specialized connectivity along its longitudinal axis. The anterior hippocampus connects preferentially to the amygdala and orbitofrontal cortex to regulate emotion and stress, while the posterior hippocampus connects to the retrosplenial and posterior parietal cortices to support cognitive and spatial processing.1