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Our brain continuously spins out thoughts, whether we want it to or not. When unwanted thoughts keep occurring, despite our efforts to control them, they feed a cycle of rumination that’s at the heart of depression and anxiety disorders. New research shows what’s going on in the brain when those unwanted thoughts occur, and why some brains are better at controlling them than others.
Most research has focused on the brain’s executive control center, the prefrontal cortex, as the area responsible for managing thoughts – both the directed kind and the persistent, intrusive kind. The latest research took a different approach by looking to the brain’s memory region for answers.
Participants completed a task known as the Think/No-Think procedure, in which they learned a series of paired but unassociated words (like “roach/ordeal” and “moss/north”). They were then presented with either a green or red signal while being shown one of the words. When the signal was green, they were asked to recall the paired word; when it was red they were asked to stop themselves from recalling it.
While this was happening, the research team analyzed the participants’ brains with a combination of fMRI (brain imaging) and magnetic resonance spectroscopy, which measures chemical changes.
The results showed that concentrations of the neurotransmitter GABA in the hippocampus, a brain area central to memory, made all the difference as to whether someone was able to manage the unwanted thought from materializing.
GABA is an “inhibitory” neurotransmitter that maintains balance in the brain by decreasing activity in neurons triggered by “excitatory” neurotransmitters. We already knew that GABA levels are central to anxiety conditions, and now it appears they also play a significant role in how well we’re able to manage intrusive thoughts.
"What's exciting about this is that now we're getting very specific," said professor Michael Anderson, from the University of Cambridge, who lead the study. "Before, we could only say 'this part of the brain acts on that part', but now we can say which neurotransmitters are likely important - and as a result, infer the role of inhibitory neurons - in enabling us to stop unwanted thoughts."
While the study wasn’t focused on identifying treatments, knowing the role GABA plays in thought management could point to more effective treatments for anxiety, depression and other conditions.
"Most of the focus has been on improving functioning of the prefrontal cortex," professor 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."
But before you think about taking a GABA supplement to fortify thought management, keep in mind that there's very little evidence that those supplements pass the blood-brain-barrier to deliver benefits, nor are they in a form that the brain can use even if they could make it through. There is, however, an evidenced-based reason to believe that high fat diets decrease GABA concentrations in the prefrontal cortex and hippocampus.
The study was published in the journal Nature Communications.
