Summary: A new NYU study shows that, over time, the brain organizes individual experiences by their shared features, forming clusters that may support conceptual knowledge.
Source: NYU
Neuroscientists at New York University report that our brains reorganize experiences across time, grouping memories by similarity.
Researchers led by Lila Davachi, associate professor in NYU’s Department of Psychology, together with Alexa Tompary, a recent NYU doctoral recipient, examined how memories change with time and how the brain represents commonalities across separate experiences. Their paper appears in the journal Neuron.
The team asked whether memories for distinct episodes become organized according to overlapping information, such as a shared scene or context, and how that organization affects the fidelity of individual memories.
In the experiment, participants learned a series of object–scene associations. Each object (for example, a tennis racket) was paired with one of four repeating scene images (such as a beach scene). Participants viewed many such pairings on a computer screen. The researchers tested participants’ memory for which object had been paired with which scene at two time points: immediately after learning and again one week later. While participants performed recall, the researchers recorded patterns of brain activity associated with individual memories.
The neural data revealed a clear change in how memories were represented. Immediately after learning, activation patterns for objects that had been paired with the same scene did not show meaningful overlap. In contrast, one week later those activation patterns became more similar in two key brain regions: the hippocampus and the medial prefrontal cortex (mPFC). In other words, over time the brain began to cluster memories that shared features, reflecting a reorganization based on similarity.
Importantly, the study also found that this grouping of related memories was associated with reduced fidelity of individual memory reinstatement. As related memories became more organized into overlapping neural patterns, the distinct activation signatures that corresponded to specific episodic details were diminished. This observation highlights a trade-off: as the brain extracts commonalities and forms higher-level groupings, memory for fine-grained, episode-specific details can weaken.
“It is as if in order to make sense of the world, the brain re-organizes individual distinct experiences into information clusters — perhaps signaling the emergence of conceptual knowledge,” said Lila Davachi. Alexa Tompary added that the findings illustrate a tension between maintaining precise memories of each event and learning the regularities that link multiple events: “If we remember each individual experience exactly as it occurred, are we able to effectively learn about the underlying regularities across experiences? We see evidence for this competition in our neural analysis of memory structures in the brain.”
The results contribute to an important question in memory research: how do episodic experiences transform into more generalized knowledge over time? By showing that the hippocampus and mPFC exhibit more overlapping activation for related memories after a delay, the study provides neural evidence for a process in which individual episodes are reorganized into clusters that highlight shared features. This reorganization may support the formation of concepts and schemas by emphasizing patterns that recur across different experiences.
These findings have implications for understanding how learning and memory operate in everyday life, where we must both retain specific experiences and extract common patterns that guide future behavior. The observed trade-off between detailed recall and generalized organization suggests memory processes that balance specificity and generality depending on the demands of learning and prediction.
About this neuroscience research
Funding: The research was supported by a grant from the National Institute of Mental Health (R01MH097085).
Source: James Devitt — NYU
Image source: NeuroscienceNews.com image in the public domain.
Original research: The study appears in Neuron.