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What is the theta rhythm 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 theta rhythm is a relatively high-amplitude brain wave pattern, typically ranging between approximately 4 and 10 hertz, that is characteristic of the hippocampus.12

This oscillation is critical to hippocampal function, particularly during spatial navigation and memory processing. The rhythm is regulated by cholinergic input from the medial septum, a region that helps set this oscillatory state. The importance of this rhythm is underscored by the fact that abolishing the medial septum or the associated theta rhythm interferes with the hippocampus's ability to function properly.23

While theta oscillations are a prominent feature of the hippocampal-entorhinal system, it is important to note that oscillations in the same frequency band can be generated by different mechanisms in other brain structures.2