Abstract
The purpose of the present study was to examine the influence of personality traits on the impact of emotional stimuli focusing on n-back task performance and brain activity changes. Previous neuroimaging studies have reported that individual differences in emotional processing can be attributed to personality traits, which is linked to the hemisphere-specific activity of the dorsolateral prefrontal cortex (DLPFC) in response to emotional stimuli. Thirty right-handed healthy young male participants were recruited in this study and classified into two groups, the behavioral inhibition system (BIS) group and behavioral activation system (BAS) group, based on their scores on the BIS/BAS scale. Participants saw six emotional images (two each with negative, neutral, and positive valence), which were selected from the International Affective Picture System and validated in a preliminary experiment. Then, a dual 2-back task that simultaneously employed auditory-verbal and visuospatial stimuli was conducted. Additionally, the concentration of oxygenated hemoglobin (Oxy-Hb) changes in the DLPFC was measured during the image presentation and dual 2-back task by near-infrared spectroscopy (NIRS). The task performance showed a significantly increased reaction time (RT) in the negative valence independent of personality traits. The results of Oxy-Hb changes showed a significant interaction between personality traits and emotional valence. Further, the hemisphere-subgroup analysis revealed that the right DLPFC activity was significantly higher in the negative valence than in the neutral valence in the BIS group; the right DLPFC activity was also significantly higher in the BIS group than in the BAS group in the positive valence. There was no main effect or interaction in the left DLPFC activity. These findings suggest the importance of considering personality traits when examining the impact of emotional stimuli. Further studies with large sample sizes warranted to examine the influence emotional stimuli exert on working memory performance, considering the personality traits to better understand individual differences in emotional processing.
Highlights
Cognitive control, a process that can inhibit automatic responses and support adaptive responses and goal-directed thought, can influence attention and memory (Dolcos and McCarthy, 2006; Dolcos et al, 2011; Inzlicht et al, 2015)
The post hoc test showed significantly higher ∆oxygenated hemoglobin (Oxy-Hb) concentration in the right dorsolateral prefrontal cortex (DLPFC) in the negative compared with the neutral valence condition in the BIS group and significantly higher ∆Oxy-Hb concentration in the right DLPFC in the BIS compared with BAS group in the positive valence condition. *p < 0.01
Task performance showed a significantly increased reaction time (RT) in the negative valence condition independent of personality traits
Summary
A process that can inhibit automatic responses and support adaptive responses and goal-directed thought, can influence attention and memory (Dolcos and McCarthy, 2006; Dolcos et al, 2011; Inzlicht et al, 2015). Previous neuroimaging evidence has indicated asymmetrical activation of the DLPFC in response to emotional stimuli; stimuli with negative emotional valence, i.e., that are intrinsically aversive, preferentially activate the right DLPFC and those with positive emotional valence, i.e., that are intrinsically attractive, preferentially activate the left DLPFC (Ortony et al, 1990; Tomarken et al, 1990; Wheeler et al, 1993; Solomon and Stone, 2002; Davidson, 2003; Russell, 2003; Balconi et al, 2017) These results suggest the importance of focusing on the interaction between prefrontal functional lateralization and stimulus emotional valence
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