For the first time, scientists, including one of Indian-origin, have seen evidence of where the brain records the time and place of real-life memories, with the help of smartphones strapped around volunteers’ necks.
Results showed that the similarity of the brain activation patterns when memories were recalled was an indicator of the breadth of space and time between the actual events.
Participants in the study wore a smartphone around their neck with an app that took random photos for a month.
Later, when the participants relived memories related to those photos in an fMRI scanner, researchers found that a part of the brain’s hippocampus stores information about where and when their specific memories occurred.
In fact, the study showed that the further apart the memories occurred in space and time, the farther apart the memories’ representations appeared in the hippocampus.
“What we’re picking up here is not the whole memory, but the basic gist u2013 the where and when of the experience,” said Per Sederberg, senior author of the study and assistant professor of psychology at Ohio State University.
“We found that the hippocampus represents time and space for at least a month of memories spanning up to 30 kilometres in space,” Sederberg said.
“It is the first time we’ve been able to study memories on the scale of our lives,” said Sederberg, who led the study with Dylan Nielson, a PhD graduate of Ohio State.
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 lifeblogging app. The app would take 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 an fMRI 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.
The researchers, including Vishnu Sreekumar of Ohio State, compared fMRI data on pairs of images for each participant. The photo pairs chosen were taken at least 100 meters and 16 hours apart.
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.
The study was published in the journal PNAS.