After analysing with an app, participants who wore a smartphone around their neck, scientists have seen for the first time evidence of where the brain records the time and place of real-life memories.
The study involved nine women aged 19 to 26 who wore an Android-based smartphone on a strap around their neck for one month.
The phone was equipped with a custom life-blogging app that took photos at random times of the day, recording the time, location, whether the person was moving and other information.
Over the course of the month, the phone took an average of about 5,400 photos for each participant.
After the month was over, the participants were placed in a brain scanner that measured activity in their brain while they were shown 120 of their own photos.
Participants were asked to try to remember the event depicted in each picture and relive the experience in their mind while viewing the photo for eight seconds.
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The researchers compared scan data on pairs of images for each participant.
The photo pairs chosen were taken at least 100 metres and 16 hours apart.
The brain scans revealed that a part of the brain's hippocampus area stores information about where and when their specific memories occurred.
The results showed that the further apart the memories occurred in space and time, the farther apart the memories' representations appeared in the hippocampus.
"What we are picking up here is not the whole memory but the basic gist - the where and when of the experience," said Per Sederberg, assistant professor of psychology at Ohio State University and senior author of the study.
Remembering an experience "lights up" many parts of the brain but different memories create different patterns of activity.
The more different two memories are, the more different the pattern of activity will be.
Results showed that patterns of activity in the left anterior hippocampus were more different for memories of events that happened further apart in time and space.
"If the participants didn't recall the images, we didn't see this relationship," Sederberg added.
Hippocampus is one of the first areas of the brain to degrade in Alzheimer's disease.
"The patients can't retrieve memories because they can't get the right general cue to get to that memory," he explained.
Sederberg hopes to repeat this experiment with people of different ages and with people who are showing early signs of dementia to see how their brains are representing their memories.
The paper was published in the journal Proceedings of the National Academy of Sciences.