New Discoveries about Spatial Memory

Our ability to recall past events, even distant ones, reflects a stability of memory and the parts of our brain responsible for it. On the other hand, new experiences integrating into old ones indicate memory plasticity.

In the hippocampus, spatial representations also show the same duality: short-term stability, and drift in the long term. According to Prof. Dori Derdikman from the Ruth & Bruce Rappaport Faculty of Medicine, “We hypothesized that experience, more than the passage of time, is the driving force behind representational drift. We compared the stability of place cells’ representations of mice traversing two similar, familiar tracks for different durations. We found that the more time the animals spent actively traversing the environment, the greater the representational drift, regardless of the total elapsed time between visits.”

Prof. Dori Derdikman (Photo credit: Ellie Lev Eitan)

Dorgham Khatib

Dr. Genela Morris

The researchers’ conclusion is that spatial representation is a dynamic process related to the ongoing experiences within a specific context, and is related to memory update rather than to passive forgetting. “Our study shows that memory drift is connected to using our memories,” says Prof. Derdikman. “If we stand in a room, we recall previous visits, and our brain might update how we remember this room. On the other hand, when we’re at a different place, our memory of that room doesn’t change.” There are practical implications to these findings. For example, in treating traumatic memories; to change the memory of a traumatic event, it must be recalled. Otherwise, it remains frozen in memory, and the trauma can’t be treated.