Interplay of episodic and semantic memory arises from adaptive compression

Sensory experiences are encoded as memories — not as verbatim copies, but through interpretation and transformation. Rate Distortion Theory (RDT) frames this process as lossy compression, aligning with numerous experimental findings. Despite its successes, RDT has a glaring problem: it assumes environmental regularities are known and unchanging, dismissing surprising experiences as noise. However, the brain's model of environmental regularities (semantic memory) is continually learned and refined, with surprising events playing a pivotal role. In this Perspective, we highlight the relevance of this challenge for structure learning and argue that adaptively learned compression fosters characteristic curriculum sensitivity, which has been a recent focus of learning research. We suggest this process provides novel insights into the role of episodic memory in preserving experiences in a relatively raw format for later interpretation. Our Perspective offers a normative framework for the interplay between semantic and episodic memory, encompassing memory distortions, curriculum effects, and prioritised replay.