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Scientists locate chemical that helps suppress unwanted thoughts

Often in the confusing and hectic place that is our mind, we find ourselves faced with unwanted thoughts about unpleasant memories. When this occurs, we don’t always have the ability to ignore these uncomfortable reminders.

In a new study, scientists have identified a key chemical within the “memory” region of the brain that helps us suppress unwanted thoughts. These findings may help explain why people who suffer from conditions such as anxiety, post-traumatic stress disorder (PTSD), schizophrenia, and depression experience constant intrusive thoughts that they have no control over.

“Our ability to control our thoughts is fundamental to our wellbeing,” says Michael Anderson from the Medical Research Council Cognition and Brain Sciences Unit at the University of Cambridge. “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 goes on to point out that these are all major symptoms of the previously mentioned mental illnesses.

In this study, a team of researchers led by Anderson and Dr. Taylor Schmitz used a task known as “Think/No-Think” in order to determine a new brain process that allows the prefrontal cortex to inhibit our thoughts. The prefrontal cortex is a region at the front of the brain that is known to play a role in controlling our actions, and acts on other brain regions as well.

The task involved participants learning to associate a series of words with a paired – but unconnected – word. Some examples of this would be ordeal/roach and moss/north. They were then asked to recall the associated word if the cue was green, or suppress it if the cue was red.

The researchers used a combination of functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy in order to analyze what was occurring in key regions of the brain when the participants were attempting to inhibit their thoughts. The spectroscopy allowed the researchers to measure brain chemistry along with the imaging being observed through the fMRI.

The results revealed that our ability to inhibit unwanted thoughts hinges on a certain neurotransmitter, which is a chemical in the brain that allows messages to pass between nerve cells. This neurotransmitter is known as GABA, and is the main inhibitory neurotransmitter in the brain. It was discovered that GABA concentrations within the hippocampus – the key area of the brain involved in memory – determine an individual’s ability to block the retrieval process and prevent thoughts from returning.

“Where previous research has focused on the prefrontal cortex – the command center – we’ve shown that this is an incomplete picture,” explains Anderson. “Inhibiting unwanted thoughts is as much about the cells within the hippocampus – the ‘boots on the ground’ that receive commands from the prefrontal cortex. If an army’s foot-soldiers are poorly equipped, then its commanders’ orders cannot be implemented well.”

The researchers believe that these findings may help determine the mechanisms behind schizophrenia, as well as other conditions that exhibit elevated activity in the hippocampus, such as PTSD, anxiety, and chronic depression. Further studies may one day lead to more effective treatments for individuals that suffer from these debilitating conditions.

By Connor Ertz, Staff Writer

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