روان رنجوری فرونتال تغییرپذیری عدم تقارن نوار مغزی در حالت استراحت را پیش بینی می کند

Research has shown that high levels of neuroticism (i.e. emotional lability) are related to emotional upset, sensitivity to negative affect, and worry. In addition, previous studies have found conflicting evidence that right frontal hemispheric activation is related to neuroticism/negative affect. Accordingly, this study investigated the relation of neuroticism to variability in frontal asymmetry within college students in the attempt to better understand the relation between frontal asymmetry and neuroticism. As predicted, higher levels of neuroticism were associated with greater mid-frontal asymmetry variability. This finding may explain, in part, why researchers have reported inconsistent results regarding the relation of neuroticism to right frontal activation and provide a novel measure that may be helpful in predicting and identifying related psychopathology.

Neuroticism (N) is an extremely robust personality trait (Zuckerman, Kuhlman, Joireman, Teta, & Kraft, 1993) that has been associated with an increased sensitivity to fear, anxiety, and distress. Those who score high on neuroticism scales have been described as more “labile,” possessing more negative affect than their “stable” counterparts (Hagemann, Naumann, Lurken, Becker, Maier, & Bartussek, 1999). These individuals are more responsive to emotional stimuli and possess a low threshold for negative affect (Smith, Kline, Lingren, Ferro, Smith, & Nespor, 1995). Studies have shown that items tending to load highly on neuroticism include emotional upset, tension, worry, and obsessive indecision (Zuckerman et al., 1993), similar to trait anxiety. Neuroticism appears to be a construct related to many forms of psychopathology, including mood and anxiety disorders (Clark & Watson, 1991a). It is composed of several facets, including anxiety, hostility, depression, self-consciousness, impulsiveness, and vulnerability. Not surprisingly, neuroticism (N) and negative affectivity (NA) have been shown to correlate highly across numerous samples (Hagemann et al., 1999 and Watson & Clark, 1992), such that NA comprises a central and organizing feature of N. Abbreviated as NA/N, this factor has been described as a “general distress factor” that is stable and heritable (Clark, Watson, & Mineka, 1994). In the Tripartite model of anxiety and depression (Clark & Watson, 1991b), NA/N is posited to be a general factor that is associated with high levels of both anxiety and depression (Clark & Watson, 1991a). Other researchers have investigated the relation between these personality constructs and psychophysiological measures, including hemispheric asymmetry in the electroencephalogram (EEG). The literature on frontal asymmetry has undergone a substantial metamorphosis since its inception. What began as a theory of positive and negative emotion (valence model) has evolved in the face of data to a motivational model pertaining to behavioral approach and behavioral withdrawal (see Davidson, 1995; Davidson, Jackson, & Kalin, 2000). Positive emotions, as well as negative yet approach-related emotions are typically associated with relative left-frontal and anterior-temporal activity,1 while negative, withdrawal-related emotion has been associated with higher relative activity of the right frontal and anterior-temporal regions (Ahern & Schwartz, 1985, Davidson, 1995, Harmon-Jones & Allen, 1997, Heller, 1990 and Tomarken et al., 1990). A substantial portion of the EEG research has focused on the hypothesis that resting anterior asymmetry relates to a stylistic tendency toward emotional reaction that is present during infancy and early childhood (Davison & Fox, 1989 and Fox et al., 1995). Anterior asymmetries recorded during baseline conditions have been used to predict emotional responses and have been correlated with personality traits. In addition, left frontal activity has been associated with personality factors related to decreased vulnerability to depression (Harmon-Jones & Allen, 1997, Kline et al., 1998, Kline et al., 1999 and Tomarken & Davidson, 1994), whereas relative left frontal hypoactivity has been associated with increased vulnerability to depression (Davidson, 1995 and Henriques & Davidson, 1990). Based on the literature linking N with NA and measures of depression, one might predict that N would also be associated with relative right-frontal activation. However, investigators have reported inconsistent results in this area. In general, studies within the normal population have not been particularly successful in linking N with psychophysiological measures of activation (see Eysenck, 1990, for a review). Kline, Blackhart, and Joiner (2002) found no correlation between N and frontal asymmetry. However, right hemisphere lesions have been associated with higher levels of N, suggesting that N might be related to the under-activation of the right hemisphere (Flor-Henry, 1969). This is consistent with another study that reported an association between N and a relatively less activated right hemisphere (Gale, Edwards, Morris, Moore, & Forrester, 2001). These findings contradict the general conceptualization of left versus right frontal asymmetry, which would lead one to predict an association between N and relative right frontal activity. Because the literature in this area is inconsistent, other factors need to be explored that might better conceptualize the relation between frontal asymmetry and N. Inconsistencies have been documented in the relation between EEG frontal asymmetry and N, or NA. One study reported that high levels of N and NA were both related to increased hemispheric asymmetry, although high N was associated with decreased activity in the right hemisphere while NA was associated with increased activity in the left hemisphere (Gale et al., 2001). Tomarken, Davidson, Wheeler, and Doss (1992) found that NA was associated with relative right frontal activity in “stable” individuals, though no significant correlations were found between NA and frontal asymmetry in “unstable” individuals. Hagemann et al. (1999) found that although N and NA were highly correlated, high levels of NA were associated with more left anterior temporal activity while high levels of N were not significantly associated with frontal asymmetry. There is evidence to suggest that these inconsistencies documented in past research might be partially explained by differences in methodology (Davidson, 1998), though other factors might be involved as well. The methodological differences are highlighted in Table 1. In this study, however, we chose to investigate a factor that is conceptually distinct from those in previous research in an attempt to help account for some of these inconsistencies. Table 1. Overview of studies investigating the relation between N/NA and frontal asymmetry Authors Number of baselines/length Referencing Number of sessions Results Gale et al. (2001) Unknown Linked mastoids One NA (induced with stimulus faces) associated with increased activity in left hemisphere; N (measured by EPQ) associated with decreased activity in right hemisphere Hagemann et al. (1999) Eight/60 s Off-line computer averaged Mastoids One NA (measured by PANAS—GEN Form) associated with more left temporal activity; N (measured by EPQ) and NA not associated with frontal asymmetry Kline et al. (2002) Six/60 s Linked ears One N (measured by EPQ) not significantly associated with frontal asymmetry Tomarken et al. (1992) Eight/60 s Averaged ears Two NA (measured by PANAS—GEN Form) not significantly associated with frontal asymmetry in unstable individuals; NA associated with more right frontal activity in stable individuals Table options Research relating different types of anxiety to EEG asymmetry suggest that individual differences in the amount of anxious arousal versus anxious apprehension experienced by individuals may lead to fluctuations in frontal asymmetry. Anxious arousal, sometimes referred to as somatic anxiety, is characterized by pounding heart, dizziness, sweating, and shortness of breath. This type of anxiety might be apparent in individuals experiencing panic attacks and has been associated with greater right frontal activity (Nitschke, Heller, Palmieri, & Miller, 1999). Anxious apprehension, or worry, on the other hand, is associated with worry over fears and negative expectancies and often involves verbal rumination. This type of anxiety may be associated with relatively greater left frontal activity (Borkovec et al., 1998, Carter et al., 1986 and Heller et al., 1997). As previously noted, anxiety is a central facet of N (Trull, 1992) and has been related to N in many studies (Clark & Watson, 1991a). Perhaps those with high levels of neuroticism experience both anxiety types, which might be reflected in inconsistent frontal asymmetry patterns. Studies have typically neglected the variability of frontal asymmetry in favor of the mean asymmetry, though substantial variability may be an important measure in itself and could be associated with certain personality characteristics, as well as psychopathological vulnerabilities. As differential patterns of hemispheric EEG activation have been associated with different emotions, perhaps variability in EEG asymmetry is related to a tendency toward fluctuation between positive and negative emotional states, or between approach and withdrawal-related motivational states. Alternatively, this fluctuation might be related to shifts between anxious arousal and anxious apprehension. In summary, researchers have reported inconsistent patterns of frontal asymmetry associated with neuroticism and related psychopathology, such as anxiety (Hagemann et al., 1999 and Nitschke et al., 1999). However, past research suggests that neuroticism is robustly associated with both anxiety and depression (Clark & Watson, 1991a). Because neuroticism has been conceptualized as a personality trait involving high levels of negative affectivity as well as fluctuating levels of emotionality, or lability, we hypothesized that those scoring high in neuroticism would exhibit greater variability in frontal EEG asymmetry.