What does it mean to describe the hippocampus as an index for distributed memories?

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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.

Describing the hippocampus as an index for distributed memories refers to a specific theoretical model of how the brain manages information. In this view, the hippocampus does not store the actual content of an experience itself. Instead, it functions similarly to an index at the back of a book, containing a set of pointers or references that bind together the various elements of an experience.1

Under this hypothesis, the actual details of a memory—such as sensory information, emotions, and context—are stored in a distributed fashion throughout other regions of the brain, particularly the cortex. The hippocampus acts as the central mechanism that links these disparate pieces of information together, allowing the brain to reconstruct the unified experience during recall. This model contrasts with theories suggesting that the hippocampus is the primary site of long-term storage, proposing instead that it serves as a critical organizational structure for accessing memories that are physically represented elsewhere.1