Everyone has a few bad memories that seem to resurface when we least expect them, usually despite our best efforts to banish those excruciating moments from the mind altogether.
For some, though, bad memories are more than embarrassing — they’re traumatic, bordering on debilitating. That’s true for returning service members and victims of abuse who suffer from post-traumatic stress, as well as for patients with debilitating anxiety, depression or even schizophrenia.
But now, scientists say they have found the key chemical that helps our brains inhibit those unwanted, intrusive memories. That’s a big deal, because the discovery could help pioneer new ways to help people get past debilitating thoughts, according to a new study published in Nature Communications this week.
So what’s the key? It’s a neurotransmitter called GABA — a chemical in the brain that sends messages between nerve cells, according the study’s author, Michael Anderson, a professor at the University of Cambridge.
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Anderson and the rest of his research team revealed in the study that GABA levels within the hippocampus — a vital part of the brain when it comes to memory — are strong predictors of whether or not you can block unwanted thoughts from resurfacing.
Think of GABA as foot soldiers in the hippocampus, Anderson said in a statement. Their mission? To block your intrusive thoughts.
You and your brain’s prefrontal cortex (the brain’s “master regulator”) are the commander of that brigade of neurotransmitter troops, the researchers wrote. But if you don’t have enough GABA soldiers on the ground in your hippocampus to block the things your prefrontal cortex doesn’t want to think about, you’re probably going to keep thinking about them.
“When this capacity breaks down, it causes some of the most debilitating symptoms of psychiatric diseases — intrusive memories, images, hallucinations, ruminations, and pathological and persistent worries,” Anderson said.
Particularly important in this research, according to the study, is the discovery of just how vital the hippocampus is in controlling intrusive thoughts.
“What’s exciting about this is that now we’re getting very specific,” Anderson said. “Before, we could only say ‘this part of the brain acts on that part’, but now we can say which neurotransmitters are likely important.”
Previous studies looked primarily to the prefrontal cortex instead of the hippocampus. As the brain’s “master regulator,” the prefrontal cortex controls many other parts of the brain, the researchers said, including the hippocampus and memories.
“Most of the focus has been on improving functioning of the prefrontal cortex,” Anderson said. “But our study suggests that if you could improve GABA activity within the hippocampus, this may help people to stop unwanted and intrusive thoughts.”
To complete the study, researchers asked participants to remember pairs of seemingly unrelated words, the BBC reported — like “ordeal” and “roach,” or “moss” and “north.”
Then, researchers would show the participants one of those words in either green or red font.
If a participant saw a word in green, he or she was supposed to think of the word it had been associated with. But if a word was in red font, participants were supposed to willfully forget which word it was associated with.
So if a study participant saw “ordeal” in green font, he or she was supposed to think “roach.”
On the other hand, if a participant saw “moss” in red font, he or she was supposed to do everything possible not to think “north.”
Meanwhile, the researchers were watching their brain activity and brain chemistry — and that’s how they discovered that GABA concentrations in the hippocampus were key to suppressing memories, according to the study in Nature.
And while the study doesn’t propose an treatments to put this new understanding into action, researchers said it could lead to a variety of new approaches down the road.