By Sam Rydberg-Cox, Winter 2021.

Every morning we must immediately make decisions. Do I get out of bed or do I hit the snooze button? What do I want for breakfast? These types of questions fill our days, but how do we actually go about choosing one option or the other? It turns out that in order for our brains to make a decision, it has to turn itself off. It seems counterintuitive, but if there are too many signals being sent to a region of the brain, it becomes overwhelmed and less productive.

Within our brain, the specific processes that underlie  our ability to make complex decisions remain unknown, but we do know which regions of the brain are activated when we face a decision. Recently, this knowledge has allowed researchers to look further into what mechanisms facilitate decision-making. To do this, a research group in Colorado examined the relationship that exists between an individual’s level of neural inhibition and their ability to make decisions. [1] 

The level of neural inhibition is essentially the extent to which the activity of certain neurons are being suppressed during a given  process. This study looked specifically at the role of gamma-aminobutyric acid (GABA) within the brain. GABA is a chemical that is known to cause neural inhibition. It exists within neurons and can be released onto specified target neurons through interneurons, which serve as connective pathways for communication between neurons. A more technical way to think about neural inhibition is the activity levels of GABA-ergic interneurons. These interneurons exist in only a single brain region and therefore have natural restrictions on the scope of their impact on brain function. [2] This supports the findings of the aforementioned research because, when neural inhibition was increased, there was not  a  significant effect on overall brain function or thought processes.

The results of the study from Colorado make it clear that neural inhibition is directly correlated with our ability to make complex decisions. [1] The researchers discovered this correlation by giving human participants a noun and asking them to produce a verb that they associate with the original word. Throughout these trials, they varied the difficulty by changing how easy it would be for subjects to retrieve the noun from their memory and how many possible verbs they would have to choose from. The study focused on how long it took each participant to generate a corresponding verb and used this “reaction time” to quantify how easy the decision was. Following   human trials, the researchers used this data to create a model of the brain and tracked its responses to different decision-making tasks. [1] 

This model allowed the researchers to have precise control over neural inhibition and allowed them to  clearly see the impacts that these changes had on decision making. [1] What they found was that when neural inhibition increased, it became much easier to make much harder choices. [1] Furthermore, when neural inhibition was decreased, it became much more difficult to make these same choices. [1] Not only does this study reveal the importance of neural inhibition in our ability to make choices, but it also offers valuable insight into what may cause people to struggle with  making large decisions. 

This insight centered around the relationship between these findings and our knowledge of anxiety disorders. A common characteristic of those with anxiety is that they find it very difficult to choose between multiple options, which is also known as experiencing decision making anxiety. The fact that symptoms appear repeatedly in anxious people suggests that it is a result of some underlying neurological traits. [3] The prefrontal cortex is largely responsible for decision making, but it must work in conjunction with the other frontal lobes–specifically, the orbitofrontal cortex and the ventromedial prefrontal cortex. [4] When all three of these cortices are working together properly, our brain works as usual. However, people with anxiety have decreased activity in these parts of the brain. [4]

Initially, this may seem to contradict the findings of the study above. While this study  claims  that the brain cannot make decisions when these areas of the brain are overworked, this anxiety research claims  that anxious people have decreased activity in the region of the brain responsible for making decisions. However, there is another factor to the equation that must be considered: the three frontal cortices affect decision making in different ways. The portion directly responsible for decision making sits on the left side of the frontal lobe, while the rest of the lobe works to regulate impulses or reward processing–both important factors in some decisions, but not the direct cause of our choices. As a result, these two seemingly contradictory facts actually come together to support each other. Since the language research only focused on the left portion of the brain, the decreased neural inhibition that was found only applies to that respective region of the brain. Overall, however, there is an increase in brain activity; it is simply not occurring in the specific portion of the brain that directly regulates decision making.

This newfound knowledge combines insights into decision making and anxiety which may in turn open doors regarding  a better understanding of decision-making anxiety. Additionally, this knowledge  could provide new ideas for clinical treatment methods and, upon further analysis, give us a better understanding of what therapy treatments will be the most effective in treating decision-making anxiety. [5]

1. Snyder, Hannah R., Natalie Hutchison, Erika Nyhus, Tim Curran, Marie T. Banich, Randall C. O’Reilly, and Yuko Munakata. 2010. “Neural Inhibition Enables Selection during Language Processing.” Proceedings of the National Academy of Sciences 107 (38): 16483–88. 
2. Freund, Tamas, and Szabolcs Kali. 2008. “Interneurons.” Scholarpedia 3 (9): 4720..
3. Catherine A. Harltley and Elizabeth A. Phelps. 2012. “Anxiety and Decision-Making.” Biological Psychiatry 72 (2): 113–18. 
4. Martin, Elizabeth I., Kerry J. Ressler, Elisabeth Binder, and Charles B. Nemeroff. 2009. “The Neurobiology of Anxiety Disorders: Brain Imaging, Genetics, and Psychoneuroendocrinology.” The Psychiatric Clinics of North America 32 (3): 549–75.
5. Yuko Manakata. 2010. “Decreased Neural Inhibition Makes Decision Making Harder For The Anxious.” Neuroscience News (blog). September 15, 2010. https://neurosciencenews.com/decreased-neural-inhibition-anxiety-decisions-neuropsychology/.