Episodic & semantic memory

In the brain

Two systems, first distinguished by Tulving: episodic memory holds specific events (“I met her Tuesday”); semantic memory holds general knowledge (“I know her”)^{Tulving 1972}. Over time, repeated episodes shed their verbatim detail and leave gist — Fuzzy-Trace Theory holds the two as parallel traces, the verbatim one fading faster^{Brainerd 2002}.

Whether semantic memory is just compressed episodes or a separate abstraction is unsettled⚖.

The model

Verbatim-to-gist degradation: detailed traces decay quickly while the extracted meaning persists. You keep “we argued about consciousness” long after the exact words are gone. Consolidation is the process that does the distilling.

In AI

engram tagged each memory episodic or semantic and, during consolidation, compressed aging episodics into semantic gist with a small model; Counterparts keeps the split but promotes a memory to the semantic band on strength alone, with no model in the loop, and merged memories are born semantic. Microsoft’s layered working/episodic/collective memory and Alai Vault’s episodic/semantic tiers cover the split. One honest caveat: real semantic memory is gist across many episodes, not one old episode squeezed down.