Singular Memories

I have noticed a memory phenomenon that I haven't heard discussed. Memory is normally discussed in terms of persistence. There are at least three layers of memory: sensory, short term, and long term. As is often the case, wikipedia has an excellent primer on this, http://en.wikipedia.org/wiki/Memory. What I have noticed is what I will call a singular memory. This is a specific long term memory where we only remember one of a series.

The quintessential example of what I call a singular memory is the combination for a lock. If you ever went to school in the United States, you undoubtedly owned a series of combination locks. Every day you unlocked the lock, perhaps several times. If you ask someone the combination of the lock they had two years ago, they probably will not remember it. It is as though there is one spot in memory for a lock combination and remembering a new one erases, or at least substantially dims the memory of the old one.

Another example is parking spots. When you park your car at a store, you remember its location for hours. This implies that the memory is long term. on the other hand, if I asked you where you parked at the same store two weeks ago, you may have no recollection at all.

Though I call this a singular memory, in fact it is not completely singular. One year at school I absent-mindedly wandered to a locker I had several years before. I was in the middle of dialing the combination I had for that locker before I realized I was in the wrong place. In the same way, if I remind you of exactly what you bought at the store two weeks ago or an incident that occurred on the way out the door, you may remember where you parked the car that day.

I believe that these singular memories may be a byproduct of the mechanism of recall. Memories are not replayed. They are reconstructed. This reconstruction is a mini re-enactment where the neurons involved in the original experience are re-activated. During this reconstruction the original memory is subject to change. I think that when we memorize a new combination for a lock, it is as though we misremembered the old combination and re-stored the new combination as the original memory. When I wandered to my old locker, I was not just trying to remember a combination, I had the entire sensory experience of an earlier year. That sensory experience triggered the original memory in context as opposed to the more abstract number whose memory was normally reinforced by a new locker location and other details.

To summarize I have proposed a new type of memory, a singular memory. I gave a couple of examples, then demolished part of my own argument by showing that the memories are not actually singular. Finally I proposed a mechanism that might explain how this type of memory, which may not exist, works.