Memory and Location, Location, Location

When you remember first meeting the love of your life, do you also have a strong memory of where you both were and also where you were in relation to objects in the scene? When I first met my wife, Doris, it was at a party and she was at a piano surround by “bird dog” males, who I saw from an adjacent room. In my mind’s eye, I still see both rooms and where everybody was.

Do you remember where you were on 9/11? I was in the waiting room of a hospital, looking over a series of lounge chairs at a large-screen TV program that was reporting the news.

It seems that many people remember not only events but where they were at the time of the event. But how does this happen? We do know that a new experience may be “consolidated” into a lasting memory, especially if it stirs emotion and you replay it in your mind. That is certainly the case when you meet the love of your life or see a terrible event.

If you were there, you would surely remember what you were doing.

Back in the 1970s I was studying the part of the brain known as the hippocampus, and it was known at the time that this structure is crucial for consolidating memories. I and others were focused on an EEG rhythm (theta rhythm of 4-7 waves per second) that was especially prominent when an animal moves around in an enclosure EEG signals are summed over dozens of neurons, and therefore to get more precise data some investigators put microelectrodes into the hippocampus so they could monitor the nerve impulse activity of single neurons as the animal moved around.

It was quickly discovered that some hippocampal neurons fired impulses selectively when an animal was in a special location within the enclosure. Collectively, these “place” neurons were actually mapping the enclosure space and tracking the animal’s position as it moved around in this space.

New insight on an additional role for place neurons has come from a new research report on human epileptics with electrodes implanted in their hippocampus to locate the diseased tissue. These patients played a virtual-reality game in which their avatar drove through a virtual town and delivered items to stores. Their task was to memorize the layout and what was delivered at each store. Meanwhile, place cells in the hippocampus were monitored and their place coding was noted. Then when participants were asked to recall the memory of what went where, the place-responsive activity was reinstated even though the subjects were not actually playing the game but recalling it from memory. And the activity of place cells was similar to that during the learning stage.

In other words, neural representations of the content of the experience had become linked with the spatial and temporal context. Such evidence provides strong evidence for the theory that memory formation and recall involve association of event with context, especially spatial and temporal context. This linkage creates a mutually reinforcing interaction of event and location. We tend to remember both or neither.

Can we apply these findings to improving everyday learning and memory situations? Of course, we can. The key elements for making it easier to learn something new are to:

1.  Identify a context that stirs emotions, preferably positive emotions like meeting someone you are attracted to.

2.  Be especially aware of where you are at the time and where you are in relation to the location of various objects.

The hippocampus uses these emotional and spatial cues to facilitate the consolidation of memory. We know that memory is promoted by making associations. Emotions and spatial cues are probably the most effective kinds of cues.

Sources: Miller, J. F. et al. (2013) Neural activity in human hippocampal formation reveals the spatial context of retrieved memories. Science. 342, 1111-1114

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