What is the trisynaptic circuit in the hippocampus?

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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 trisynaptic circuit is one of the two principal neural pathways within the hippocampus that facilitates the flow of information through its subregions.

The circuit operates through the following sequence:

Entorhinal Cortex to Dentate Gyrus: Information is first forwarded from the entorhinal cortex to the dentate gyrus via the perforant path.
Dentate Gyrus to CA3: Information then travels from the dentate gyrus to the CA3 region through the mossy fibre pathway.
CA3 to CA1: Finally, information is transmitted from CA3 to CA1 along bundles of axons known as Schaffer collaterals.

The circuit is completed by outbound projections that return to the subiculum and the entorhinal cortex.1