A team of scientists from the University of Cambridge (United Kingdom) has identified a key chemical within the brain, specifically in a region of memory that allows us to suppress unwanted thoughts, which would help explain why people suffering from Anxiety disorders, post-traumatic stress disorder (PTSD), depression and schizophrenia , often experience persistent obsessive thoughts when these circuits are not well.
Sometimes we are faced with reminders of unwanted thoughts: perhaps about an unpleasant memory or something that worries us.
“Our ability to control our thoughts is fundamental to our well-being. When this capacity is broken down, it causes some of the most debilitating symptoms of psychiatric illness: obsessive memories, images, hallucinations and pathological and persistent concerns. These are all the key symptoms of mental illnesses such as schizophrenia or depression,” explains Michael Anderson, co-author of the journal Nature Communications.
The rapid reflexes that help us stop a fall or trip over something or someone, exist in the same way in the brain in order to avoid the repetition of unwanted thoughts.
To identify this brain mechanism of the prefrontal cortex (which plays a key role in controlling our actions and our thoughts), scientists used a task known as the “think / not think” procedure.
In the task, the participants learn to associate a series of words with a paired word, but without connection, for example bird-south and moss-north. In the next phase, they should remember the associated word if the signal is green or suppress it if the signal is red; thus, by showing them ‘bird’ in red, they were asked to look at the word but not to remember the associated thought ‘south’.
Using a combination of functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy, the researchers were able to see what was happening in the key regions of the participants’ brain as they tried to inhibit their thoughts. Spectroscopy allowed the researchers to measure brain chemistry, and not just brain activity, as is generally done in imaging studies.
The researchers showed that the ability to inhibit unwanted thoughts is based on a neurotransmitter, a chemical inside the brain that allows messages to pass between nerve cells, known as GABA. Concentrations of GABA within the hippocampus, a key area of the brain involved in memory, predicted people’s ability to block the recovery process and prevent the return of thoughts and memories.
“The exciting thing about this is that we are now becoming very specific, we could only say ‘this part of the brain acts in that part’, but now we can say which neurotransmitters are important and, as a result, infer the role of inhibitory neurons , by allowing us to stop unwanted thoughts, “says Anderson.
This discovery may answer one of the historical questions about schizophrenia. Research has shown that people affected by schizophrenia have a “hyperactive” hippocampus, which correlates with intrusive symptoms such as hallucinations, which shows that the hippocampus does not inhibit wandering thoughts and memories, which can manifest as hallucinations.
Experts believe they could offer a new approach to address intrusive thoughts on anxiety, schizophrenia, depression or post-traumatic stress disorder, which include a pathological inability to control thoughts.
“Most of the focus has been on improving the functioning of the prefrontal cortex, but our study suggests that if it can improve GABA activity within the hippocampus, it can help people stop unwanted and intrusive thoughts,” he concludes. Anderson