Unreachable Memories

Think back to your earliest years, before you turned 6. What do you remember?

Odds are, not much. And what you can dredge up are foggy, scattered glimpses of events, without the important when, how and why that would give context.

Why that’s true is the focus of a new study by psychology assistant professors Tracy Riggins and Elizabeth Redcay, who seek to understand how children’s brains create and retain memories.

“It’s not just a matter of forgetting,” Riggins says—it’s that these memories aren’t formed in a way that allow them to be accessed later on.

The key is the hippocampus, a critical gateway in the brain through which information passes to create memories. It’s been widely studied in adults, but not in children at such a critical age of brain development, ages 4 to 8.

Riggins and Redcay ask children about recent events like trips to visit relatives or the first day of school and prod them for specific timelines and details. The children also play memory games.

Then, the researchers take ultra-high resolution brain scans of the children using the functional magnetic resonance imaging (fMRI) machine at UMD’s Maryland Neuroimaging Center. These scans detect changes in blood flow; recently accessed portions of the brain are flooded with oxygenated blood, and areas that commonly work together appear similar.

So far, about halfway through their three-year study, they’ve found that as children age from 4 to 6, the hippocampus becomes more strongly connected to areas like the lateral temporal regions and prefrontal cortex to form clearer, more complete memories. While in adults, a larger hippocampus correlates to more robust memory abilities, in children under the age of 6, size doesn’t matter—the organization of the developing hippocampal network might be more important instead.

Being able to identify exactly when the network is mature and its typical appearance in a scan can help doctors discover problems in children at risk for memory impairment before they start school. It could also guide the treatment of those with brain damage or disorders that can lead to memory impairment, like depression or schizophrenia.