Memories of the same events co-exist at different resolutions in the brain, neuroscientists from Radboud University’s Donders Institute have shown. Coarse and fine memory scales are distributed across different parts of the hippocampus, a brain area that plays an important part in memory.

Our memories exist in different resolutions.

For example, last Friday you might remember going to work and having drinks with friends afterwards. You might also remember more detailed events like the commute to the office. Or even some very specific events like reading a particular e-mail.

Now it has been shows that these memories co-exist at different locations. To avoid interference, the finest scale memories are distributed at the back of the hippocampus and the coarser memories at the front of the hippocampus.

First author Silvy Collin says:

“We showed participants life-like events created with the videogame The Sims 3. These were integrated into multi-event narratives."

Participants watched these animated events while lying in an MRI scanner.

“We think that memories of these events are stored in different locations of the hippocampus to avoid interference when retrieving either coarse or detailed memories”, Collins explains.

Since the subjects in this study were all young, healthy adults, the next step is to investigate whether the mapping of memory resolutions works the same way in the hippocampus of people with for instance dementia.

Principal investigator Christian Doeller adds:

“We see that the various memory resolutions are formed automatically, but we believe that they can exist independent from each other."

Silvy H P Collin, Branka Milivojevic, Christian F Doeller Memory hierarchies map onto the hippocampal long axis in humans Nature Neuroscience, 2015; DOI: 10.1038/nn.4138

Illustration: Silvy Collin and colleagues

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