A joint study across three scientific institutions in Spain shows that some hippocampal neurons are responsible for preserving prior memories, even when new information about the same event is recorded.
Imagine there is a construction project in your neighborhood. The human brain has the ability to remember three different states of it: the initial state before reconstruction, the process of the work itself, and the final result after the project is completed. But how does the brain avoid mixing these three memories together?
The Institute of Neuroscience, a public research center composed of the Spanish National Research Council (CSIC) and Miguel Hernández University, believes it has identified this neural mechanism in its new study, which it published in the journal PLOS Biology (source in Spanish).
The team at the Network Plasticity laboratory believes the brain uses a part of the hippocampus called the dentate gyrus for this task, whose role is to create new memories. In this region, a specific type of neuron inhibits the activity of other cells so the brain can better register new experiences.
To demonstrate this, the research team tested this inhibitory process in mice at higher and lower intensities. Encarnación Marcus, co-leader of this study and head of this research line at the IN CSIC-UMH institute, says: “When the level of inhibition was lower than usual, the mice’s behavior was more consistent with better memory retrieval and recall of more details.”
However, there is no single fixed level of inhibition that is inherently better or worse for preserving the maximum possible amount of information. The computational model used in this experiment showed that when memory load is lower, this inhibitory activity is less beneficial for the brain, but when the volume of information increases significantly, that is no longer the case.
The study shows that depending on the type of memory, the hippocampal dentate gyrus can either facilitate the entry of new data or, conversely, hold a memory more firmly against new stimuli; a matter that depends on the contextual importance of the memory or what the team calls “task demands.” Marcus concludes: “Our interpretation of these results is that there is a mechanism that, using inhibition, dynamically adjusts the way the network functions.”