Stress-related dysfunction of the right inferior frontal cortex in high ruminators: An fNIRS study

Repetitive thinking styles such as rumination are considered to be a key factor in the development and maintenance of mental disorders. Different situational triggers (e.g., social stressors) have been shown to elicit rumination in subjects exhibiting such habitual thinking styles. At the same time, the process of rumination influences the adaption to stressful situations. The study at hand aims to investigate the effect of trait rumination on neuronal activation patterns during the Trier Social Stress Test (TSST) as well as the physiological and affective adaptation to this high-stress situation. Methods A sample of 23 high and 22 low ruminators underwent the TSST and two control conditions while their cortical hemodynamic reactions were measured with functional near-infrared spectroscopy (fNIRS). Additional behavioral, physiological and endocrinological measures of the stress response were assessed. Results Subjects showed a linear increase from non-stressful control conditions to the TSST in cortical activity of the cognitive control network (CCN) and dorsal attention network (DAN), comprising the bilateral dorsolateral prefrontal cortex (dlPFC), inferior frontal gyrus (IFG) and superior parietal cortex/somatosensory association cortex (SAC). During stress, high ruminators showed attenuated cortical activity in the right IFG, whereby deficits in IFG activation mediated group differences in post-stress state rumination and negative affect. Conclusions Aberrant activation of the CCN and DAN during social stress likely reflects deficits in inhibition and attention with corresponding negative emotional and cognitive consequences. The results shed light on possible neuronal underpinnings by which high trait rumination may act as a risk factor for the development of clinical syndromes.