A new brain imaging study has found that recalling facts and personal experiences activates nearly identical neural networks, challenging long-held views on memory systems. Researchers from the University of Nottingham and University of Cambridge used fMRI scans on 40 participants to compare these memory types. The results, published in Nature Human Behaviour, suggest a rethink in how memory is studied and could inform treatments for Alzheimer's and dementia.
Scientists have long distinguished between episodic memory, which involves reliving specific past events like a personal milestone at a certain time and place—often called "mental time travel"—and semantic memory, which stores general facts and knowledge untethered from their learning context. However, a recent study questions this separation at the neural level.
Led by Dr. Roni Tibon, an assistant professor at the University of Nottingham's School of Psychology, in collaboration with the Cognition and Brain Sciences Unit at the University of Cambridge, the research involved 40 participants performing matched memory tasks. In one, they recalled real-world associations between logos and brand names, testing semantic memory. In the other, they remembered pairings learned during the experiment, engaging episodic memory. Functional magnetic resonance imaging (fMRI) tracked brain activity by measuring blood flow changes during these retrievals.
The scans revealed no significant differences in brain activation between the two tasks, showing strong overlap in the regions involved. fMRI works by detecting increased oxygen-rich blood to active areas, producing 3D images of brain engagement.
Dr. Tibon expressed surprise at the findings: "We were very surprised by the results of this study as a long-standing research tradition suggested there would be differences in brain activity with episodic and semantic retrieval. But when we used neuroimaging to investigate this alongside the task based study we found that the distinction didn't exist and that there is considerable overlap in the brain regions involved in semantic and episodic retrieval."
She highlighted potential implications for neurological conditions: "These findings could help to better understand diseases like dementia and Alzheimer's as we can begin to see that the whole brain is involved in the different types of memory so interventions could be developed to support this view."
Traditionally, these memory types have been studied separately, limiting direct comparisons. Dr. Tibon advocates for a shift: "Based on what we already knew from previous research in this area we really expected to see stark differences in brain activity but any difference we did see was very subtle. I think these results should change the direction of travel for this area of research and hopefully open up new interest in looking at both sides of memory and how they work together."
The study, titled "Neural activations and representations during episodic versus semantic memory retrieval," appears in Nature Human Behaviour (DOI: 10.1038/s41562-025-02390-4).
