Scientists have looked at the brain waves of mice to tell old memories apart from new ones, with implications for treating brain damage.
A team from Japan’s Riken Centre for Brain Science (CBS) has analysed recordings from the brains of mice using a machine learning algorithm to determine whether a memory occurred recently or a long time ago.
The ability to identify the location and persistence of memories in the brain has major implications for the treatment and understanding of brain damage, memory loss and clinical memory impairments.
In the research published to Cell Reports, the team said that it found robust communication between a frontal brain region – the anterior cingulate cortex (ACC) – and the hippocampus, an area strongly involved in memory formation.
As part of the study, researchers recorded interactions between the two brain areas before they sent a small shock through a foot of each of the mice to form a memory. They would then follow this up with another shock in the same cage both one day and one month later.
If the mice froze after being shocked a second time, it was an indication they remembered it from before. Neuronal recordings revealed that the ACC and hippocampus – specifically an area dubbed CA1 – are highly synchronised when mice recall the fear memory.
Tracking the age of memories
Over time, the interactions between the two brain areas changed. ACC and CA1 activity became more correlated when an old memory was recalled versus a more recent, one-day memory.
“While memory is consolidated over time in frontal areas, we think in this case the ACC is facilitating the retrieval of contextual details back from the hippocampus,” said senior author Thomas McHugh.
“We could decode whether a mouse was recalling a recent or remote memory by looking at the correlations in ACC-CA1 interactions.”
Looking to further research, this discovery may form a mechanism that would allow us to track the age of memories.
“While we have known for 20 years that the ACC is important for recalling older memories, how it contributes has remained a mystery,” McHugh said.
“We found that it plays an important role in organising activity in the hippocampus, the part of the brain in which the memory was originally formed. This suggests the hippocampus always plays a role in providing key details of an old experience, at least in the healthy brain.”