Brain Mechanism for Updating Memories Without Confusion Identified in Hippocampus Study

Consider a neighborhood construction site. The human brain can distinctly recall three phases: the pre-renovation state, the construction process, and the completed structure. Yet the neurological mechanism preventing these sequential memories from blurring together has remained unclear.

Researchers at the Institute of Neurosciences—a joint center of the Spanish National Research Council (CSIC) and Miguel Hernández University—have now pinpointed this process in a study published in PLOS Biology. The team, working in the Neural Network Plasticity laboratory, found that the dentate gyrus, a subregion of the hippocampus responsible for generating new memories, employs a specific class of inhibitory neurons to gate the integration of fresh experiences.

In experiments with mice, scientists modulated this inhibitory activity. “With lower-than-usual levels, their behaviour was more consistent with better memory retrieval and a more detailed recollection,” explains Encarni Marcos, co-lead author and head of the research line at IN CSIC-UMH. However, the study reveals no universally optimal inhibition level. Computational modeling demonstrated that reduced inhibition enhances memory precision under light cognitive loads, but becomes detrimental as information volume increases substantially.

The findings indicate the dentate gyrus dynamically switches operational modes depending on memory type and contextual demands—either prioritizing the encoding of new inputs or stabilizing existing traces against interference. “What we infer from these results is that there is a mechanism that dynamically adjusts the mode of operation by using inhibition,” Marcos concludes.

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