Neurotransmitter can curb unwanted thoughts

Patients who suffer from mental disorders such as depression, post-traumatic stress disorder (PTSD) and anxiety have minds that work differently from others.

Scientists know that the onset of these disorders is most likely linked to a specific region of the brain, a concept known as “localization.” After many years of research, scientists have been able to identify this region as the prefrontal cortex, which is a sophisticated structure that resides within the frontal lobe of the brain and regulates many complex behaviors such as voluntary movement and motivation.

Furthermore, researchers have recently pinpointed a specific chemical released in the brain that directly controls how the human mind deals with excessive and otherwise undesired emotions.

It is normal for people to occasionally be troubled with overwhelming thoughts, especially during stressful or difficult times. However, revisiting these unwanted memories and thereby re-immersing themselves in negative emotions could lead to many deleterious effects on people’s mental health. More often than not, negative thoughts that are persistent and lingering raise a red flag for mental disorders.

Why are some people worse at handling or repressing their thoughts than others, and how does this tie into the mental processes underlying day-to-day neural functions?

It turns out that there is a group of researchers out there who utilized a technique known as the Think/No-Think task to investigate this very question.

The research group is co-led by Michael Anderson and Taylor Schmitz, both professors from the Medical Research Council Cognition and Brain Sciences Unit at the University of Cambridge.

The Think/No-Think task can be explained in very simple terms. In the task, participants are given various pairs of words that are not connected in any noticeable way. For example, they could be given the task of learning to remember word pairs such as “ordeal/roach” and “moss/north.”

After this initial stage of forming concrete associations, participants are then asked to do one of two things. If a word with a green cue appears on the screen, they should recall the associated word. Conversely, if the cue is red, they should try their best to suppress the associated word.

Going back to the example, this would mean that if the word “ordeal” is shown in red, the participants would have to stare at the word but try to suppress the retrieval of the associated word, “roach.”

Using this simple yet powerful technique, Anderson and his team began examining images that reflect neural activities using both functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy (MRS).

The combination of these two imaging techniques is highly informative. It not only gave researchers a direct gateway to observing what areas in the brain are associated with the inhibition of thoughts, but it also allowed the researchers to measure brain chemistry, which spectroscopic analyses were instrumental for.

The team’s study showed that the brain’s ability to inhibit unwanted thoughts relies heavily on a neurotransmitter called GABA. GABA is categorized as one of the brain’s main inhibitory neurotransmitters, which acts to suppress neural excitability in the brain.

Anderson’s team discovered that the presence of GABA in the hippocampus is directly indicative of a person’s ability to halt the retrieval of thoughts.

“What’s exciting about this is that now we’re getting very specific,” Anderson said in an interview with the BBC.

The team published their new findings in a recent edition of the journal Nature Communications. Their research is funded by the Medical Research Council.

This research has shed light on the potential origins of a broad range of conditions such as depression, PTSD and anxiety.

Although the researchers have not yet looked into the possibility of any treatments, Anderson believes that further studies of how to improve the functions of the prefrontal cortex could serve as a promising starting point.