Neural Correlates of Emotion-Related Impulsivity
Post by Leanna Kalinowski
The takeaway
The structure of the orbitofrontal cortex is associated with the severity of emotion-related impulsivity, which has previously been implicated in the development of several mental disorders.
What's the science?
Occasional instances of impulsivity – acting suddenly without careful thought – are a normal part of human behavior. Some manifestations of impulsivity, however, are a hallmark sign of several mental disorders. Particularly, emotion-related impulsivity (ERI) – experiencing a frequent loss of control during strong emotion states, such as giving into cravings or saying regrettable things when upset – is consistently associated with mental disorders including depression, anxiety, and substance use disorders. Despite the well-known association between ERI and mental disorders, there is little known about how ERI is represented in the brain. This week in Biological Psychiatry, Elliott and colleagues studied whether the structure of brain regions responsible for emotion and control is associated with ERI severity.
How did they do it?
The researchers recruited 122 participants with two different displays of psychopathology: individuals with internalizing psychopathology (i.e., disorders where negative emotions are kept internal, such as depression), and individuals with externalizing psychopathology (i.e., disorders where negative emotions are externalized, such as conduct disorder). Psychopathology was assessed through structured clinical interviews.
Impulsivity in these individuals was measured using the Three Factor Impulsivity Index, which consists of two subscales that measure ERI and a third subscale that was a measure of non-emotion-related impulsivity. The authors used this third subscale as a control comparison.
All participants also underwent structural magnetic resonance imaging (MRI) to examine the structure of several brain regions of interest that are known to regulate emotion: the orbitofrontal cortex, insula, amygdala, and nucleus accumbens. Within these regions, the researchers calculated cortical thickness along with the Local Gyrification Index, which measures how much of the brain’s surface is buried in sulci (i.e., the grooves in the cerebral cortex).
What did they find?
First, the researchers found an association between ERI and the structure of the orbitofrontal cortex. Specifically, individuals with higher ERI had lower gyrification in the orbitofrontal cortex, meaning that these individuals have a smoother cortex and smaller cortical surface area in this brain region. There was no association between ERI and the other three brain regions that were examined. Second, when comparing the structure of the orbitofrontal cortex across the brain’s two hemispheres, the researchers found that an imbalance in gyrification was associated with ERI severity. Specifically, individuals with greater orbitofrontal gyrification in the left hemisphere compared to the right hemisphere had greater ERI severity. Finally, the researchers found no association between non-emotion-related impulsivity and brain structure in these regions.
What's the impact?
This study was the first of its kind to directly investigate the association between ERI and gyrification in the brain. Taken together, these results demonstrate that the structure of the orbitofrontal cortex – specifically, the smoothness of its surface – is associated with ERI severity. These results may help pave the way for developing mental health treatments that more directly target the orbitofrontal cortex in individuals with severe ERI.
