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Can You Trust Your Memory? This Neuroscientist Isn’t So Sure:

There are three kinds of memory that all work together to shape your reality. Neuroscientist André Fenton explains.

In 2011, Andrē Fenton and Todd Sacktor, professor of neurology at the SUNY Downstate Medical Center, came up with a theory that suggested a molecule called PKMzeta altered neurons in the brain to form long-term memories. They came to this conclusion by observing the behaviour of rats and mice. First, they let their test subjects loose in a small arena and let them discover that certain areas of the enclosure would deliver shocks to their bodies. They quickly learned to avoid those routes.

Then, they injected their subjects with genetic elements called ZIP that would block PKMzeta. After receiving the injections, the rodents did not recall which routes shocked them, suggesting that their memories had been wiped and that PKMzeta played an important role in memory formation.

Some scientists questioned these findings and conducted their own experiments. Richard Huganir, the director of the Department of Neuroscience at the Johns Hopkins University School of Medicine, created a group of genetically engineered mice that couldn’t produce PKMzeta. He and his colleagues found that these rodents could produce long-term memories without the presence of PKMzeta, contradicting Fenton and Sacktor’s theory. Furthermore, when they injected them with ZIP their memories were erased, suggesting another molecule could be responsible for making memories since PKMzeta wasn’t present.

Despite these contradictory findings, Fenton and Sacktor continued their research and found that another molecule, PKC-iota-lambda (iota for short), was very similar to the structure of PKMzeta. But instead of originating in the brain, it’s found all over the body and is used by cells to move proteins. In their initial research, they recorded that iota was present in rodents' early stages of memory formation but that it quickly disappeared. Since their theory was being disputed, they dug further into iota and found that there were high levels present in the animals where PKMzeta was blocked.

Following this discovery, they gave the PKMzeta-depleted mice a dose of a chemical that stopped iota from forming and found that they couldn’t pass their memory tests. The theory was that iota continued to grow in the neurons due to the lack of PKMzeta, taking on the role of memory formation. They then tested these two molecules against each other and found that iota wasn’t nearly as strong as PKMzeta when it came to animals performing complex memory tasks.

If you thought mice brains were complex, you might want to strap yourself in for what’s going on in your head.

“I can’t trust my memory,” says Fenton, who is especially interested in the hippocampus and how it controls how we choose relevant information to process. “When we experience the world, we are using our brains, and the brain is a self-organizing system. Through its own use, it gets modified, so we’re not simply reproducing what it is that we have experienced – we’re reconstructing. We are building a new experience, and we tend to build those experiences according to the stories that make sense to our minds.”

In the human brain, there are approximately 100 billion neurons, all with varying abilities to communicate with the neurons they are connected to.

These connective synapses usually grow stronger through continued use and weaken when rarely used. “The strengthening and the weakening of those synapses is an active biochemical process that makes those adjustments,” Fenton says. “And when those adjustments persist, that’s what we call memory.”

When these memories continue across different categories of information, that’s what we call a mindset – something that Fenton explains is integral to how we engage with and remember our environment.

Cognitive psychologists knew long ago that mindset was crucial to how we perceive the world and remember things from the world,” he says. “We can all experience what would appear to be the same thing. Look down the street. Everyone will focus their attention on different aspects of what’s available for them to recollect. Naturally, we can have a different recording of these events. So when we retell these stories, we reconstruct those events from fragments of our memory and build stories around our mindset.”

So, how do we find truth and honesty in a world where we all interpret events differently? Fenton advises we all accept our shortcomings and keep an open mind.

“Recognise that we all have a distorted perception and that later we will have a distorted understanding and recollection of the perception called memory,” he says. “If you fundamentally believe that, it demands you act in the world with a certain sense of humility and empathy for others. When new evidence or a new point of view appears, be ready to consider it.”