Damee Choi

Seasonal variation of non-shivering thermogenesis (NST) during mild cold exposure

BackgroundThe physiological function of non-shivering thermogenesis (NST) has been investigated in recent years, and some studies have discussed the importance of NST with respect to human cold adaptation. The present study aimed to clarify individual and seasonal variations in NST that occurred as a result of mild cold exposure.MethodsSeventeen male university students participated in the present study during summer and winter. The climate chamber used was programmed so that ambient temperature dropped from 28°C to 16°C over an 80-min period. Physiological parameters of test subjects were recorded during the experiments.ResultsIncreases in oxygen intake (VO2) during cold exposure were significantly greater without shivering in winter than they were in summer. Respiratory exchange ratio (RER) was significantly lower during thermoneutral baseline and cold exposure in winter than it was during the same periods in summer. In addition, there was a significant negative correlation between ΔVO2 and ΔRER.ConclusionsIncrease of VO2 without shivering indicated increase of NST, and decrease of RER depends on the metabolization of fat in winter. These results suggested that NST activity was activated by seasonal acclimatization, and individual variation of NST depends on individual variation of fat metabolism.

Does cigarette smoking relieve stress? Evidence from the event-related potential (ERP).

Previous studies have reported a paradox that cigarette smoking reduces stress psychologically; however, it increases the arousal level physiologically. To examine this issue, our study aimed to investigate whether cigarette smoking relieves stress by measuring the late positive potential (LPP), a component of the event-related potential (ERP). In Experiment 1, participants first watched emotionally neutral images; second, they received a break; and finally, they watched emotionally neutral images again. In the break, they smoked a cigarette (smoking condition) or simply rested without smoking (non-smoking condition). The procedure of Experiment 2 was the same as that of Experiment 1, except that the participants watched unpleasant images as stress stimuli before the break. In Experiment 1, the LPP decreased from before to after the break in the smoking condition, but not in the non-smoking condition, suggesting that smoking cigarettes in the neutral state reduces the arousal level. In Experiment 2, the LPP for 400-600 ms decreased from before to after the break, both in the smoking and non-smoking conditions; however, the LPP for 200-400 ms decreased from before to after the break only in the smoking condition. This suggests the possibility that cigarette smoking in the unpleasant state may facilitate a decrease in the arousal level faster than with non-smoking. In both Experiments 1 and 2, the subjective rating results also suggested that cigarette smoking decreased anxiety. Taken together, both the physiological (LPP) and the psychological responses from our study suggest that cigarette smoking perhaps relieves stress.

Effect of empathy trait on attention to various facial expressions: evidence from N170 and late positive potential (LPP)

BackgroundThe present study sought to clarify the relationship between empathy trait and attention responses to happy, angry, surprised, afraid, and sad facial expressions. As indices of attention, we recorded event-related potentials (ERP) and focused on N170 and late positive potential (LPP) components.MethodsTwenty-two participants (12 males, 10 females) discriminated facial expressions (happy, angry, surprised, afraid, and sad) from emotionally neutral faces under an oddball paradigm. The empathy trait of participants was measured using the Interpersonal Reactivity Index (IRI, J Pers Soc Psychol 44:113–126, 1983).ResultsParticipants with higher IRI scores showed: 1) more negative amplitude of N170 (140 to 200 ms) in the right posterior temporal area elicited by happy, angry, surprised, and afraid faces; 2) more positive amplitude of early LPP (300 to 600 ms) in the parietal area elicited in response to angry and afraid faces; and 3) more positive amplitude of late LPP (600 to 800 ms) in the frontal area elicited in response to happy, angry, surprised, afraid, and sad faces, compared to participants with lower IRI scores.ConclusionsThese results suggest that individuals with high empathy pay attention to various facial expressions more than those with low empathy, from very-early stage (reflected in N170) to late-stage (reflected in LPP) processing of faces.

Gender difference in N170 elicited under oddball task.

BackgroundSome studies have reported gender differences in N170, a face-selective event-related potential (ERP) component. This study investigated gender differences in N170 elicited under oddball paradigm in order to clarify the effect of task demand on gender differences in early facial processing.FindingsTwelve males and 10 females discriminated targets (emotional faces) from non-targets (emotionally neutral faces) under an oddball paradigm, pressing a button as quickly as possible in response to the target. Clear N170 was elicited in response to target and non-target stimuli in both males and females. However, females showed more negative amplitude of N170 in response to target compared with non-target, while males did not show different N170 responses between target and non-target.ConclusionsThe present results suggest that females have a characteristic of allocating attention at an early stage when responding to faces actively (target) compared to viewing faces passively (non-target). This supports previous findings suggesting that task demand is an important factor in gender differences in N170.

Effect of emotional arousal on inter-temporal decision-making: an fMRI study

BackgroundPrevious research has shown that emotion can significantly impact decision-making in humans. The current study examined whether or not and how situationally induced emotion influences people to make inter-temporal choices.MethodsAffective pictures were used as experiment stimuli to provoke emotion, immediately followed by subjects’ performance of a delay-discounting task to measure impulsivity during functional magnetic resonance imaging.ResultsResults demonstrate a subsequent process of increased impulsive decision-making following a prior exposure to both high positive and negative arousal stimuli, compared to the experiment subjects’ experiences with neutral stimuli. Findings indicate that increased impulsive decision-making behaviors can occur with high arousal and can be characterized by decreased activities in the cognitive control regions such as prefronto-parietal regions.ConclusionsThese results suggest that ‘stabilization of high emotional arousal’ may facilitate a reduction of impulsive decision-making and implementation of longer term goals.

Relative left frontal activity in reappraisal and suppression of negative emotion: Evidence from frontal alpha asymmetry (FAA)

Previous studies have shown that reappraisal (changing the way that one thinks about emotional events) is an effective strategy for regulating emotion, compared with suppression (reducing emotion-expressive behavior). In the present study, we investigated relative left frontal activity when participants were instructed to use reappraisal and suppression of negative emotion, by measuring frontal alpha asymmetry (FAA). Two electroencephalography (EEG) experiments were conducted; FAA was analyzed while 102 healthy participants (59 men, 43 women) watched negative images after being instructed to perform reappraisal (Experiment 1) and suppression (Experiment 2). Habitual use of reappraisal and suppression was also assessed using the emotion regulation questionnaire (ERQ). The results of Experiment 1 showed that relative left frontal activity was greater when instructed to use reappraisal of negative images than when normally viewing negative images. In contrast, we observed no difference between conditions of instructed suppression and normal viewing in Experiment 2. In addition, in male participants, habitual use of reappraisal was positively correlated with increased relative left frontal activity for instructed reappraisal, while habitual use of suppression did not show a significant correlation with changes in relative left frontal activity for instructed suppression. These results suggest that emotional responses to negative images might be decreased for instructed reappraisal, but not suppression. These findings support previous reports that reappraisal is an effective emotion regulation strategy, compared with suppression.