Why do some past events seem to change when we remember them years later? Why can the same experience feel vivid at one moment and surprisingly altered at another? A recent comprehensive scientific review explores how memories of personal experiences are formed, stored, and retrieved – and why remembering the past does not always mean replaying it exactly as it happened. By examining memory as an active and dynamic process, the authors describe how recollections can evolve over time while remaining connected to real events.Revisiting Personal Memories Through Old Photos. Image by FreepikNote: This article is intended for general information and educational purposes. It summarizes scientific research in accessible language for a broad audience and is not an official scientific press release.A new peer-reviewed review article examines how episodic memories – memories of personally experienced events – are represented in the brain and why they often change over time. The paper was authored by Michael D. Rugg from the Center for Vital Longevity and the School of Behavioral and Brain Sciences at The University of Texas at Dallas, and Louis Renoult from the School of Psychology at the University of East Anglia in the United Kingdom. It was published in Neuroscience and Biobehavioral Reviews in 2025.Rather than treating memory as a static record of past experiences, the authors analyze it from what they describe as a representational perspective. This approach focuses on how memories exist as active and latent representations, how they are retrieved through specific neural mechanisms, and how their content can be reshaped over time. According to the authors, this framework helps clarify why memories can remain tied to real events even when their details appear to shift.What the Researchers InvestigatedThe authors set out to address a deceptively simple question: what, exactly, counts as a memory? From a cognitive neuroscience perspective, they examine how memory representations are maintained, activated, and transformed in the brain. Their primary focus is on episodic memory in cognitively healthy adults, defined as consciously accessible memories for unique, personally experienced events.A central issue explored in the review is how memories can change while still being considered memories of real past events. The authors adopt what they describe as a causal perspective, according to which a memory representation must be causally linked to an actual past event in order to qualify as a memory. At the same time, they emphasize that this causal link does not require the remembered content to be an exact copy of the original experience.The review also aims to clarify longstanding ambiguities in memory research by distinguishing between different kinds of representations, including cognitive versus neural representations and active versus latent memory states. These distinctions allow the authors to integrate findings across multiple research traditions and theoretical models.How the Study Was ConductedThe paper is a narrative and conceptual review rather than an original experimental study. According to the authors, it synthesizes findings from psychology, cognitive neuroscience, animal research, and philosophy of memory. As reported by Neuroscience News, the research team examined almost 200 psychology and neuroscience studies related to memory representations, along with relevant philosophical papers and recent studies using animal models.The review draws heavily on human neuroimaging research, particularly studies using functional magnetic resonance imaging to investigate memory retrieval and neural reinstatement. It also incorporates evidence from animal models examining engram cells, which are neural ensembles thought to encode memory traces.Throughout the paper, the authors compare and evaluate several influential theoretical frameworks, including standard consolidation theory, trace transformation theory, multiple trace theory, and constructivist accounts of memory. The stated aim is not to promote a single model, but to clarify how different perspectives can inform unresolved questions about memory representation.What Makes This Study NewThe authors emphasize that their contribution lies in bringing conceptual clarity to how memory representations are discussed across disciplines. A key element of this effort is the clear distinction between active memory representations – those that are currently accessible and influence thought and behavior – and latent memory traces, which can remain dormant until triggered by appropriate cues.Another distinguishing feature of the review is its explicit use of a causal definition of memory. According to the authors, this framework allows memory to be understood as dynamic without collapsing the distinction between remembering and imagining. They also highlight the role of retrieval processes, suggesting that remembering itself plays an important part in shaping memory content over time.Key Findings from the StudyThe study found that episodic memories are supported by neural memory traces, often referred to as engrams, which are formed when an event is experienced and can remain inactive until activated by a retrieval cue.According to the authors, the retrieval of an episodic memory involves the reinstatement of patterns of neural activity that overlap with those present during the original experience, a process strongly associated with hippocampal function.The review reports that the content of a retrieved memory is typically composed of multiple information sources, including information directly related to the original event as well as semantic, schematic, and situational information relevant at the time of retrieval.The authors describe how the act of remembering itself can lead to re-encoding, meaning that memories – particularly those of temporally remote events – may form a causal chain linking the original experience to the currently accessible memory trace.Analyses discussed in the review indicate that memory reinstatement is often incomplete, and that memories can become more abstract or schematic over time while still retaining a causal connection to the original event.Authors’ ConclusionsThe authors conclude that episodic memory should be understood as both stable and malleable. While memories must retain a causal connection to past events to qualify as memories, their content is not fixed. Instead, memory representations are shaped by encoding conditions, retrieval cues, contextual factors, and repeated acts of remembering.They suggest that retrieval-related processes, including reinstatement and re-encoding, provide a mechanistic basis for understanding how memories can change without losing their connection to the past. The authors also note that multiple memory traces may coexist rather than newer memories simply overwriting older ones.The review acknowledges several limitations, including the difficulty of directly observing memory traces in humans and the challenge of linking neural findings to subjective memory experience. According to the authors, many questions remain unresolved, particularly regarding how memory traces are modified at the cellular level and how causal links are maintained over long periods of time.Understanding the Broader ContextA summary of this research was also reported by Neuroscience News, which highlighted several central points drawn from the review. The article emphasized the dynamic nature of episodic memory and the role of retrieval cues in activating latent memory traces, as well as broader areas in which memory reshaping is relevant, based on the authors’ discussion.Key Facts: Dynamic Memories: Episodic memories are continually updated, not stored as perfect copies.Trigger-Based Recall: Hidden memory traces become conscious only when activated by cues.Real-World Impact: Memory reshaping affects mental health, education, and legal decision-making.Key Questions Answered:Why do memories change over time? Each retrieval blends original memory traces with generic knowledge and present context, reshaping the memory into a revised version of the past.What determines whether something is a “real” memory? A memory must be causally linked to an actual past event, even though the recalled version may include altered or added details.Why is this research important for everyday life? Understanding how memories evolve informs mental health treatment, supports better learning strategies, and highlights the limitations of eyewitness testimony.ConclusionThis review provides a detailed account of how episodic memories are represented in the brain and why they can change over time. By emphasizing causal links, retrieval mechanisms, and representational dynamics, the authors outline a framework that accommodates both memory stability and variability. The findings contribute to ongoing scientific discussions about how the brain maintains connections to past experiences while continually updating memory content. Further research, according to the authors, will be needed to clarify how these processes operate across different timescales and contexts.The information in this article is provided for informational purposes only and is not medical advice. For medical advice, please consult your doctor.ReferencesRugg, M. D., & Renoult, L. (2025). The cognitive neuroscience of memory representations. Neuroscience & Biobehavioral Reviews, 179, 106417. https://doi.org/10.1016/j.neubiorev.2025.106417Why Memories Change: How the Brain Rewrites the Past. Neuroscience News. University of East Anglia. https://neurosciencenews.com/episodic-memory-change-30022/The post Why We Remember the Same Events Differently Over Time, According to Science appeared first on CogniFit Blog: Brain Health News.