Scientist have found evidences of where the brain records the place and time of real-life memories. In a study published in Proceedings of the National Academy of Science, Ohio State University researchers showed that the brain patterns related to the activation of this specific region when memories were recalled were a clear indicator of the time and space between events. This could represent a significant advance for Alzheimer’s disease.
Each participant carried a smartphone app that was placed around their neck and took random photos for about a month. Later, participants were analyzed under an fMRI scanner and researchers noticed that when subjects relived the memories related to the photographs, a region of the brain’s hippocampus kept information of when and where they occurred. Moreover, the further apart those memories occurred in time and space, the further apart their representations appeared in the hippocampus.
Per Sederberg, an assistant professor of psychology at Ohio State and senior author of the study, said in a news release, “What we’re picking up here is not the whole memory, but the basic gist – the where and when of the experience. This could be viewed as the memory hub, where we have these general, large-scale representations of our experiences.”
So far, the majority of the work carried out in this field has been preformed using laboratory rats, though some human studies have also been developed. “We found that the hippocampus represents time and space for at least a month of memories spanning up to 30 kilometers (19 miles) in space. It is the first time we’ve been able to study memories on the scale of our lives,” Sederberg added.
Sederberg led the study which involved 9 women with ages between 19 and 26 who wore the smartphone for a month. The app took random photos and registered time, location and some additional information, with about 5,400 photographs for each participant taken. The subjects were then placed in an fMRI scanner in which their brain activity was measured while they observed 120 photos. They were encouraged to remember the event related to each picture and relive the experience in their mind while looking at the picture for about 8 seconds.
Researchers found that the patterns of activity observed in the left anterior hippocampus were even more discrepant for those memories corresponding to events that happened further in time and space. “If the participants didn’t recall the images, we didn’t see this relationship. We also don’t get this effect if we only asked about the time and not the place of the memory. We found that time and space are very much intertwined in our representations of memories,” Sederberg added.
The left anterior part of the hippocampus is the broad picture of where and when an event occurred while the posterior portion of the hippocampus might adjust the time and place. “What we found may be just the targeting mechanism that gives us the general gist of the memory. And then there is a process that moves out through the rest of the hippocampus and spreads out through the cortex as we relive the entirety of the memory,” he added.
This study may carry important implications for the study of Alzheimer’s disease, as the hippocampus is one of the first brain areas to degrade in these patients. “People with Alzheimer’s may forget experiences and people because they are not able to effectively target their old memories. They can’t retrieve memories because they can’t get the right general cue to get to that memory,” he concluded.