Memory? It Uses Your Brain, And Your Sight

I remember, years ago, seeing a man expose himself on a busy main street while I was out running.  I immediately went to the police station and was asked to look through a notebook of potential suspects.

I saw someone immediately who looked like the man, but we had seen a movie recently with a villain who (oddly enough) looked very similar.  Figuring that couldn't be the right man, I said I couldn't pick him out of the faces.  The cop pointed to the exact same picture and said, "Is that him?"

Now, if I were a witness on the stand who was asked the same question, a trial might have gone very differently.  (I never heard back, but clearly, he was a frequent flier!)

Turns out that many decisions we make are often influenced by our memories and the confidence we have in them.  (Don't get me started on False Memory Syndrome, that awful -- and false -- idea put forward by groups in the '90s trying to deny sexual abuse memories that surface later in life.)

But how do we decide if we can trust our memories?    Sadly, I'm in that group of people who was assailed by the False Memory Syndrome people and who, for many years, denied my own remembrance of very traumatic events from my childhood.

Then, when my memories started coming back, I doubted them, too, creating, like the recently reported molestation of sisters by their brother in the TLC series, 19 Kids and Counting, a huge dark hole of a whole period of my life.  The sisters didn't remember, too.

So how do we know if what we remember is what really happened, especially if others are trying to convince us it didn't?

Researchers have identified a unique set of neurons in an area of the brain where memories and memory-based decisions are processed. They show that the activity of these neurons is indicative of the confidence by which a memory will be retrieved.

Some people with amnesia, for example, are overconfident in their decision-making, while others are aware of their poor memories and are able to weigh their judgments accordingly, as reports.

“Because memory and judgment processes impact our everyday lives, we want our confidence level to be an accurate reflection of reality,” says Ueli Rutishauser, PhD, assistant professor of neurosurgery and director of human neurophysiology research at Cedars-Sinai, who has studied how . gained insight into the formation of memories and the way people perceive them.

But here's the rub.  Turns out one group of our brain cells simply reports what is being seen, such as a car, a tree, a dog or a house. These neurons give a running commentary on the environment, but they only respond to stimuli, regardless of whether or not the individual has seen an object before.

In contrast, a second group appears to be directly involved in memory retrieval and confidence. When a person sees something familiar, like their own dog, familiarity neurons are stimulated. When a person sees something new, like a different dog, activity of novelty neurons increases.

The upshot?  What we see -- if it's something we see all the time -- is not influenced by memory.  Sight (and perception) of familiar things is controlled by one set of neurons, while memory, another.  They're two entirely different parts of our brain.  But as the level of activity increases in both of these types of brain cells, the more confident we become in our memories and how we perceive them.

What we see when we look at something we know -- our dog, our house, our kids -- has nothing to do with our memory. These familiarity cells are completely anatomically different from our novelty neurons.

It's the level of activity in these neurons that gives us confidence in remembering what we've seen.  The more activity, the more confidence. 

So, to get back to the suspect, I might have been confused because the sight of the man's face reminded me of the man from the movie.   Both sets of neurons were involved in the retrieval of his face.  You can see why it can often be so difficult for trial witnesses to remember exactly what happened.  They're using two completely different parts of their brain!  And I need all of them. 


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