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Do you ever find yourself stuck in a rut of repetitive thinking or an infinite loop of obsessive rumination in which you replay the same thought again, and again, and again? On the flip side, do you find that spurts of repetitive thinking are an important part of your creative process and that being "obsessed" with solving a riddle is essential to having "eureka!" moments? I would answer "yes" to both questions.
For example, I'm obsessed with the cerebellum. Every day, I have my antennae up for new research that might give us new clues on how the cerebellum (Latin for little brain) and the cerebrum (Latin for brain) are intertwined. I spend a lot of time ruminating about the cerebellum and trying to connect the dots in new and useful ways. This new study is a valuable addition to solving this puzzle.
In this blog post, I explore recent neuroscientific findings on the brain mechanics of rumination and negative repetitive thinking as they relate primarily to regions of the prefrontal cortex and the default mode network (DMN).
"Rumination" is called rumination because the act of repetitive thinking is similar to the regurgitation of cud by "ruminant" animals such as goats, sheep, and cows. Depressive rumination is the compulsive focus of attention on thoughts that cause feelings of sadness, anxiety, distress, etc.
Depressive Rumination Can Hijack the Default Mode Network
Multiple studies have identified that people who are experiencing depression are more prone to rumination and repetitive thoughts of shame, anger, regret, and sorrow. A new study from Stanford University, led by Dr. J. Paul Hamilton and colleagues at the Laureate Institute for Brain Research, sheds light on the brain mechanisms giving rise to these symptoms.
The July 2015 study, “Depressive Rumination, the Default-Mode Network, and the Dark Matter of Clinical Neuroscience,” was published in the journal Biological Psychiatry.
Hamilton et al did a meta-analysis of previous research and identified that depressive ruminations are more likely to emerge when the firing and increased cerebral blood flow to a specific region of the cerebrum called the subgenual prefrontal cortex (sgPFC) synchronizes with the default mode network (DMN).
The default mode network (DMN) is a network of brain regions that are active when your mind wanders and you find yourself daydreaming, reminiscing, or lost in self-referential thought. On an EEG, the brain typically appears to be in a wakeful state of rest when the DMN is activated. The DMN is characterized by coherent neuronal oscillations at a rate lower than 0.1 Hz (one every 10 seconds).
The researchers believe that increased connectivity between the sgPFC and DMN can backfire by creating a vicious cycle of rumination in people who are experiencing depression. In an editorial comment, Dr. John Krystal, editor of Biological Psychiatry said,
This study shows that depression distorts a natural process. It would seem that normally the subgenual prefrontal cortex helps to bias the reflective process supported by the default mode network so that we can consider important problems in the service of developing strategies for solving them.
However, in depression it seems that the subgenual prefrontal cortex runs amok hijacking normal self-reflection in a maladaptive way. This may be one reason that electrical stimulation of the sgPFC is helpful for some patients with severe or treatment-resistant symptoms of depression.
Using this new model, the Stanford researchers propose that increased functional connectivity between sgPFC and the DMN in major depressive disorder (MDD) represents an integration of the self-referential processes supported by the DMN that creates a neural network that is linked to depressive rumination.
This study raises interesting questions about the roots of depression and the correlation vs. causation of rumination. Does this association suggest that depression causes rumination or vice versa? Either way, breaking apart the connectivity of the sgPFC and the DMN when someone is depressed would have positive benefits.
What are some potential ways to break the cycle of rumination by disrupting the connectivity of the sgPFC and the DMN? I have a hunch that taking a dual-pronged approach that involves either mindfulness or dynamic proprioceptive activities that engage the cerebellum might "unclamp" the prefrontal cortex's grip on the DMN and allow for stream of consciousness thinking and less rumination.
Last week, I wrote a Psychology Today blog post, "The Neuroscience of Savoring Positive Emotions," based on a study that found a link between activation of the ventral striatum and sustained positive moods.
In many ways, rumination is the opposite of savoring positive emotions. Another possible way to break apart the brain connectivity linked to depressive rumination might be daily practices that activate the ventral striatum.
Why Does Depressive Rumination Inhibit Cognitive Function?
A recent study found that individuals who self-identified as being in a depressive mood had a 12 percent reduction in working memory in comparison to individuals not experiencing a depressive mood. It's important to clarify that a depressive mood is much different than a major depressive disorder.
The January 2015 study, "Depressive Thoughts Limit Working Memory Capacity in Dysphoria," was published in the journal Cognition and Emotion. The research was conducted at the Center for BrainHealth at The University of Texas at Dallas and was the first to substantiate memory deficits in individuals with depressed mood. In a press release, lead author Nicholas Hubbard explained the study, saying:
The results suggest that individuals with and without depressed mood generally have a similar ability to actively remember information. However, when depressive thoughts are present, people with depressed mood are unable to remove their attention from this information, leading to deficits in their memory. Our findings implicate that therapeutic approaches such as teaching one to recognize and inhibit depressive thoughts could be a key aspect to treating cognitive deficits in depression.
The study included 157 undergraduate students. All participants completed a computer-based depression inventory that measures self-reported, depressive symptoms experienced over the previous two-weeks. A total of 60 participants were classified as having depressed mood and 97 as having non-depressed mood.
Depressive rumination can feel like you're a lab rat on a running wheel to nowhere. How can you break the cycle of negative rumination? Based on a simple split-brain "up-down" model between the cerebellum and cerebrum (which houses the sgPFC), I believe that activities that engage the cerebellum and unclamp the prefrontal cortex might be directly linked to breaking obsessive or compulsive rumination.
Yesterday, I wrote a Psychology Today blog post, "Want to Improve Your Cognitive Abilities? Go Climb a Tree!" based on a new study which found that physical activities requiring dynamic proprioception (such as climbing a tree or balancing on a beam) can increase working memory by up to 50 percent.
These findings on proprioception support my hypothesis and educated guess that engaging the cerebellum and "unclamping" the prefrontal cortex is key to improving working memory and creativity.
Conclusion: Does Rumination Stagnate Imagination?
The latest neuroscientific research on rumination and repetitive thinking helps us understand the brain mechanics of dwelling on negative thoughts. From a positive psychology perspective, there are infinite benefits to breaking free from rut-like thinking, including the ability to be creative and connect ideas in new and useful ways.
In my next Psychology Today post, I'll explore how a better understanding of the brain mechanics involved in rumination or repetitive thinking can facilitate creativity and imagination when coupled with an "unclamping" of your prefrontal cortex. Stay tuned!
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