A team of scientists from the University of Cambridge (United Kingdom) has identified a key chemical within the brain, specifically in a memory region that allows us to suppress unwanted thoughts, which would help explain why people who suffer from Anxiety disorders, post-traumatic stress disorder (PTSD), depression and schizophrenia, often experience persistent obsessive thoughts when these circuits are not right.
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 critical to our well-being. When this ability breaks down, it causes some of the most debilitating symptoms of psychiatric illness: obsessive memories, images, hallucinations, and persistent pathological worries. These are all key symptoms of mental illnesses such as schizophrenia or depression “, explains Michael Anderson, co-author of the work to 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 prevent unwanted thoughts from being repeated.
To identify this brain mechanism in the prefrontal cortex (which plays a key role in controlling our actions and our thoughts), the scientists used a task known as the “think / not think” procedure.
In the task, participants learn to associate a series of words with a paired but unconnected word, for example bird-south and moss-north. In the next phase, they must 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 ‘southern’ thought.
Using a combination of functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy, the researchers were able to observe what was happening in key regions of the participants’ brains as they tried to inhibit their thoughts. Spectroscopy allowed 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 relies on a neurotransmitter, a chemical within the brain that allows messages to pass between nerve cells, known as GABA. GABA concentrations 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 now we are getting very specific. Before, we could only say ‘this part of the brain acts on 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 an “overactive” hippocampus, which is correlated 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 in anxiety, schizophrenia, depression, or post-traumatic stress disorder , including 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 you can improve GABA activity within the hippocampus, you can help people stop unwanted and intrusive thoughts.” Anderson.
Referencia: Taylor W. Schmitz et al, Hippocampal GABA enables inhibitory control over unwanted thoughts, Nature Communications (2017). DOI: 10.1038/s41467-017-00956-z
