Have you ever wanted to stop ruminating on something and just been unable to?
Scientists could have the secret. They have identified a chemical in the brain's "memory" region that allows us to suppress unwanted thoughts.
The discovery may help explain why some people can't shift persistent intrusive thoughts - a common symptom of anxiety, post-traumatic stress disorder (PTSD), depression and schizophrenia.
Researchers say controlling our thoughts is "fundamental to wellbeing".
Prof Michael Anderson, from the University of Cambridge, who conducted the study, said: "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."
Participants were asked to learn to associate a series of words with a paired, but otherwise unconnected, word - for example ordeal/roach and moss/north.
After this, they had to respond to either a red or green signal. If it was green, they were expected to recall the associated word but if it was red, they were asked to stop themselves from doing so.
Their brains were monitored using both functional magnetic resonance imaging (FMRI), which detects changes in blood flow, and magnetic resonance spectroscopy, which measures chemical changes in the brain.
Image copyright Newscast Online Image caption The study may help explain why some people can't shift persistent intrusive thoughts
Researchers found a particular chemical, or neurotransmitter, known as Gaba, held the key.
Gaba is the brain's main "inhibitory" neurotransmitter. That means, when it's released by one nerve cell it suppresses the activities of other cells to which it is connected.
They found people who had the highest concentrations of Gaba in their brain's hippocampus (or memory hub) were best at blocking unwanted thoughts or memories.
"What's exciting about this is that now we're getting very specific," said Prof Anderson.
"Before, we could only say 'this part of the brain acts on that part', but now we can say which neurotransmitters are likely to be important."
The discovery might shed light on a number of conditions, from schizophrenia to PTSD, in which sufferers have a pathological inability to control thoughts - such as excessive worrying or rumination.
Prof Anderson believes the findings could offer a new approach to treating these disorders. "Most of the focus has been on improving functioning of the prefrontal cortex," he said.
"Our study suggests that if you could improve Gaba activity within the hippocampus, this may help people to stop unwanted and intrusive thoughts."
xxkoloblicinxx on November 3rd, 2017 at 16:06 UTC »
Wait this is a symptom of anxiety?
I have anxiety, but I never realized it wasnt normal to have intrusive thoughts linger for hours or even days...
Mehofjack on November 3rd, 2017 at 14:36 UTC »
For those curious, the real interesting findings of this study imo is the actions of GABA in the hippocampus that are distinct from the dlPFC. The dlPFC and vmPFC have anticorrelated activity, I.e. when one is up, the other is down. In depression, for example, persistsnt negative self-rumination is very common and is linked largely to the abnormally low dlPFC activity (necessary for engaging with the external world) and abnormally high vmPFC activity (necessary for introspective processes) often seen in patients with depression. Both are part of the prefrontal cortex (PFC) that projects to both the amygdala (anxiety) and hippocampus (memory and affective interpretation).
The general model has emphasized influences from the dlPFC low activity and hyperactivity of the default network, which is a network of brain regions involved in introspective processing of stimuli. The latter includes the vmPFC and sgACC. The idea is that hyperactivity of this network impairs the persons ability to recruit the dlPFC (or better yet, the fronto-parietal network) when allocating resources enabling engagment with external stimuli. This article shows, however, that the hippocampus plays a larger role in this process that is specific to GABA (the brains most abundant inhibitory neurotransmitter). We already know the hippocampus 'gates' projections from the mPFC and amygdala to brain reward centers, and that this process regulates emotional processing. But this study shows that GABA influences at the hippocampus may be a mechanism contributing to the self-ruminating components typical of disrupted affective processing.
Do note my research focuses around depression, so my context may be a bit off from the article.
EDIT: Lots of questions about treatment and clarity on the network. An easier interpretation of these results is that dysfunction of the hippocampus (I.e. low GABA) might reduce the ability of the frontal lobe (PFC, specifically the dlPFC) to engage in proper executive/cognitive processing. The dlPFC is also assoc. with 'turning down' other brain regions associated with excessive self-rumination. The idea, from my interpretation (sorry I'm on my phone and havent read the whole article), is that lower GABA levels are inhibiting the hippocampus' ability to aid in regulating this introspective processing, I.e. preventing hippocampal regulation over dlPFC processing. Im not familiar with the direct circuit between the hippocampus and dlPFC, though. It is important to note as well that this overall network is very complex, and i can't seem to identify exactly what model the authors are proposing. If you're interested, a good place to start learning is Googling "LCSPT circuits."
Also, for those assuming that taking GABA might help, it is important to remember that all drugs aimed at treating psychopathology act as 'shotguns'. If you take GABA it will influence many different things. A good example are SSRIs aimed at increasing serotonin levels. This also happens in the periphery, thus, often producing sexual dysfunction and weight gain. Please consult a specialist before taking ANYTHING (including supplements), especiialy if you are already on medication.
EDIT 2: Also a lot of people making overarching assumptions based on the findings. Two points should be noted. 1) This is a network well-established in the neuroimaging literature, and these findings (I.e. low hippocampus GABA and modulation over dlPFC) are a great addition to it. 2) An important concept to remember in neuroscience is that GABA (being the brains most abundant inhibitory neurotransmitter) does not always equal downstream inhibition. Sometimes you inhibit the inhibitor and create more excitation by disinhibting excitatory neurons. This is a exemplified by the mechanisms of ketamine and NMDA receptors. Its also similar with Glutamate (opposite of GABA acting as the brains most excitatory neurotransmitter) which might excitate the inhibitor, providing more inhibition. Thus, lower GABA might be a result of a multitude of different mechanisms. Please do not assume that 1) low GABA is causally defined here, and 2) that taking GABA or GABA agonists will help this specific circuit.
LAST EDIT: Thanks for the gold.
I'd like everyone to understand something very critical to this overall network. The main idea behind some of this research is that patients engage in excessive negative self-rumination. This does not mean self-rumination is a bad thing. Please do not think that. Self-rumination /introspection can be very beneficial if harnessed correctly. The bad part is when that affective processing hyperfocuses on the "negative" stuff. So, stay positive and think about how your better than that little devil on your shoulder. Dont let your actions or experiences determine how you define your reality.
LAST LAST EDIT: Here is a link to the peer-reviewed, open access publication.
Credit goes to /u/sublimal2 for finding the open access pub at the beginning of the thread. The comment got buried very quickly, so Thanks! This is hot off the press and published today. Exciting. Unfortunately I don't have time to read it tonight to double-check my understanding. If you notice a flaw in my understanding please let me know!
dw_jb on November 3rd, 2017 at 13:36 UTC »
Can someone clever eli5