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Why can disrupting the theta rhythm interfere with memory and hippocampal function?

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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 (4–10 Hz) is a critical oscillatory pattern that dominates the hippocampal-entorhinal system during spatial navigation and memory processing. Its regulation is largely managed by the medial septum, which provides essential cholinergic input to the hippocampus.12

Disrupting the theta rhythm interferes with memory and hippocampal function because these oscillations are fundamental to the temporal coordination of neuronal activity. Brain rhythms, including theta, serve to segregate and group neuronal activity, effectively parsing and concatenating information for communication between brain areas. By facilitating the synchronization of neurons, these rhythms allow for the efficient formation of neuronal assemblies and the successful exchange of messages.1

Because the theta rhythm is integral to the physiological state of the hippocampus, abolishing the medial septum or the rhythm itself disrupts these coordinated processes, thereby impairing the hippocampus's ability to support memory and spatial navigation.2