تفاوت های فردی در عدم تقارن EEG قدامی بین افراد تدافعی بالا و پایین در طول یک نشخوار/کار حواس پرتی

Abstract The current study examined how reactions to a negative mood manipulation and a rumination/distraction task differed between high defensive (HD) and low defensive (LD) individuals. At baseline, high defensive participants exhibited significantly greater relative left frontal EEG activity than low defensive participants. HD also exhibited greater relative left anterior activity during both the negative mood induction and during the rumination/distraction task, regardless of group assignment. Contrary to predictions, there were no differences in self-reported mood between HD and LD in either the rumination or distraction group. A significant interaction was found between gender and group, indicating that anterior alpha asymmetry patterns differed for men and women during the rumination/distraction task.

1. Introduction While most individuals are distressed by negative events, thoughts, and mood states, certain individuals seem to be immune to the effects these situations have on their everyday lives. They seemingly cope with negative events easily, often without acknowledgement of the unpleasant event. These individuals seem to ‘defend’ themselves regularly from unpleasant mood states. Research has indicated that individuals with a repressive/defensive coping style may be protected from experiencing and developing psychological disorders. Repressors tend to have an avoidant coping response to negative emotions, events, and information (especially negative information about themselves), and report using significantly more distraction strategies than low defensive individuals when faced with negative emotion (Myers, 1998). In fact, these individuals seemingly cope very well with stress and negative emotion, appear to be well adjusted, report little anxiety, depression, or hostility, and do not acknowledge having many stressors in their lives (Jamner & Leigh, 1999). Repressors also tend to deny the experience of distress and negative affect in stressful situations (Jamner & Schwartz, 1986). A repressive/defensive coping style is also related to greater relative left frontal EEG activity (Kline, Allen, & Schwartz, 1998; Kline, Blackhart, & Joiner, 2002; Kline, Blackhart, & Schwartz, 1999; Kline, Knapp-Kline, Schwartz, & Russek, 2001; Tomarken & Davidson, 1994), which may act as a protective factor against psychological illness. For instance, previous research has suggested that greater relative left frontal EEG activity is related to positive, approach related emotion, while greater relative right frontal EEG activity is related to negative, withdrawal-related emotion (see Davidson, 1998; Davidson, Pizzagalli, Nitschke, & Putnam, 2002, for reviews). Greater relative right anterior EEG activity has also been associated with depression (e.g., Allen, Iacono, Depue, & Arbisi, 1993; Gotlib, Ranganath, & Rosenfeld, 1998; Henriques and Davidson, 1990 and Henriques and Davidson, 1991; Schaffer, Davidson, & Saron, 1983) and anxiety (Bruder et al., 1997; Nitschke, Heller, Palmieri, & Miller, 1999; Wiedemann et al., 1999).1 The current study was designed to examine changes in anterior EEG asymmetry patterns and affect when those with a repressive/defensive coping style were asked to endure and process negative emotion. High defensive (HD) and low defensive (LD) individuals were first given a negative mood manipulation, and then completed either a rumination or distraction task afterwards. When asked to dwell on and ruminate about their negative thoughts and feelings, how would HD react to the task? Several studies have shown that those who engage in a ruminative response task report increased negative affect (e.g., Blagden & Craske, 1996; Lyubomirsky and Nolen-Hoeksema, 1993 and Lyubomirsky and Nolen-Hoeksema, 1995; Morrow & Nolen-Hoeksema, 1990; Nolen-Hoeksema & Morrow, 1993; Trask & Sigmon, 1999). Ruminative thoughts are symptom focused and contemplative. They focus attention on one’s emotional state, and inhibit actions that might distract a person from their negative mood (Nolen-Hoeksema, 1991). As a result, ruminative thinking can prolong negative affect and depressive symptoms. HD, however, who appear to defend themselves against negative stimuli, may react differently to a rumination task than LD. We predicted that (1) consistent with previous research, HD would exhibit greater relative left frontal EEG activity at baseline; (2) HD would display significantly greater relative left anterior activity during both the negative mood manipulation and the rumination task than LD (as HD would tend to distract themselves from the task at hand); (3) those in the distraction condition (HD or LD) would exhibit greater relative left anterior activity than those in the rumination condition; and (4) HD would report less negative affect than LD following the negative mood induction and following the rumination/distraction task.

3. Results 3.1. Effects on mood There was a significant effect for Time on the MSQ, F(1, 89) = 62.51, p < .001, indicating that mood significantly improved after completing the rumination/distraction task (T1 mean = 16.21, SD = 5.86; T2 mean = 10.73, SD = 4.92). The Group effect and Time ∗ Group interaction were non-significant, indicating there was no difference in change in mood between those in the rumination and distraction conditions. For the EPQ-L, the Defensiveness and Group effects and Defensiveness ∗ Group interaction on MSQ scores were non-significant. Results were similar for the MCSD, with only the Defensiveness ∗ Group interaction approaching significance, F(1, 89) = 3.77, p = .055. This indicates HD in the distraction group displayed the most positive change in mood following the rumination/distraction task. 3.2. Defensiveness and EEG asymmetry There were significant correlations between EPQ-L scores and averaged baseline alpha asymmetry at F4–F3, r = .26, p < .05, F8–F7, r = .33, p < .05, and T4–T3, r = .27, p < .05, and between MCSD scores and baseline alpha asymmetry at F4–F3, r = .25, p < .05, and F8–F7, r = .33, p < .05. Significant correlations were also found between EPQ-L scores and alpha asymmetry during the sad story at T4–T3, r = .24, p < .05, and between MCSD scores and alpha asymmetry at F4–F3, r = .25, p < .05, and F8–F7, r = .28, p < .05. There were also significant correlations between EPQ-L scores and alpha asymmetry during the rumination/distraction tasks at T6–T5, r = .26, p < .05, and between MCSD scores and alpha asymmetry at F8–F7, r = .27, p < .05. EPQ-L and MCSD scores significantly predicted baseline anterior alpha asymmetry patterns at the midfrontal (F4–F3; F(1, 63) = 4.61, p < .05), lateral frontal (F8–F7; F(1, 63) = 7.58, p < .01), and anterior temporal (T4–T3; F(1, 63) = 4.95, p < .05) sites (EPQ-L), and at F4–F3, F(1, 63) = 4.36, p < .05, and F8–F7, F(1, 63) = 7.71 (MSCD), where higher defensiveness scores predicted greater relative left anterior activity. EPQ-L and MCSD scores failed to predict log transformed alpha power at individual sites. EPQ-L and MCSD scores significantly predicted anterior alpha asymmetry patterns during the sad story at T4–T3, F(1, 89) = 4.63, p < .05 (EPQ-L), and at F4–F3, F(1, 89) = 5.28, p < .05, and F8–F7, F(1, 89) = 5.93, p < .05 (MCSD), where higher defensiveness scores predicted greater relative left anterior and anterior temporal activity during the negative mood induction. EPQ-L and MCSD scores again failed to predict log transformed alpha power at individual sites. For alpha asymmetry during the rumination/distraction task, there was a significant EPQ-L main effect at T6–T5, F(1, 88) = 6.32, p < .05. The EPQ-L ∗ Group interaction was significant at T4–T3, F(1, 89) = 3.94, p = .05, and T6–T5, F(1, 89) = 5.56, p < .05, indicating that those engaging in the distraction task exhibited greater relative left anterior temporal activity than those engaging in the rumination task, and that for those in the distraction group, high defensive individuals displayed greater relative left anterior temporal activity than low defensive participants. The EPQ-L ∗ Group interaction significantly predicted alpha power in the right hemisphere at T4, F(1, 89) = 10.25, p < .01, and T6, F(1, 89) = 7.37, p < .01. The main effect for Defensiveness was non-significant at T5 and T6. There was a significant MCSD main effect at F8–F7, F(1, 88) = 6.79, p < .05, and approaching significance at F4–F3, F(1, 88) = 3.08, p < .10, indicating that higher defensiveness scores predicted greater relative left frontal activity during both the rumination and distraction tasks. The Group main effect and MCSD ∗ Group interaction were non-significant. Results were non-significant for alpha power at separate electrode sites. 3.3. Gender differences Gender did not predict baseline anterior asymmetry. There was, however, a significant Defensiveness ∗ Gender interaction at F8–F7, F(1, 63) = 6.26, p < .05, and T4–T3, F(1, 63) = 8.27, p < .01, indicating that HD men (EPQ-L) displayed greater relative left anterior activity at baseline than high defensive women. Effects at individual sites were non-significant. The Defensiveness ∗ Gender interaction on baseline anterior asymmetry was non-significant when MCSD scores were entered into analyses. The Gender effect and Defensiveness ∗ Gender interaction on alpha asymmetry during the sad story were non-significant. For alpha asymmetry during the rumination/distraction task, the Gender main effect was non-significant, but the Group ∗ Gender interaction was significant at F4–F3, F(1, 86) = 5.21, p < .05, and F8–F7, F(1, 86) = 6.52, p < .02, indicating that men in the rumination group displayed greater relative right frontal activity during the task than men in the distraction group, while women in the rumination group displayed greater relative left frontal activity during the task than women in the distraction group. Again entering alpha power at separate electrode sites into analyses, results were non-significant. The Defensiveness ∗ Gender and Defensiveness ∗ Group ∗ Gender interactions on alpha asymmetry during the rumination/distraction task were also non-significant.