Selected Attentional Bias in Different Level of Trait Anxiety
2013, 45 (10):
Anxiety is one of the most common mental disorders and has attracted attention of more and more researchers. A number of behavioral studies suggest that attentional bias towards threat among anxious populations is a relatively robust phenomenon. The attentional biases are observed not only across different experimental tasks but also across different anxiety disorders. However, studies of the neural mechanisms of this phenomenon are currently rare and inconsistent. It was found that compared to low trait anxiety (LTA), high trait anxiety (HTA) evoked different P2 between angry and neutral faces, with a larger P2 to the angry face in some studies. In contrast, others found that threatening stimuli elicited a larger P2 in both groups. Similarly, inconsistent findings also exited for the P1. In addition, the N1 effect on the attentional bias to fearful images with a complex context is still unclear. Therefore, the present study aimed at investigating the electrophysiological markers of attention bias for fearful images with a complex context in anxiety. Participants were selected out of a pool of 70 undergraduate students. The participants were screend on the basis of their response to Spielberger’s Trait Anxiety Inventory. Those with scores in the top quartile of the distribution (n=17, 6 males and 11 females) were assigned to the HTA group, and those in the bottom quartile of the distribution (n=17, 10males and 7 females) were assigned to the LTA group. All participants were right-handed, and had normal or corrected normal vision. ERPs were recorded when subjects viewed 30 fear and 30 neutral pictures which were presented twice. ERP data from five midline electrode sites was selected for further statistical analysis: Fz, FCz, Cz, CPz, and Pz. We measured mean amplitudes in four windows following stimulus onset: 120~140 ms (N1), 230~250 ms (N2), 300~500 ms (P3), and 500~1000 ms (Slow wave, SW). Anxiety group (HTA vs. LTA) ×picture type (fearful vs. neutral) ×electrode sites (Fz, FCz, and Cz) analysis of variance (ANOVA) was conducted on the amplitude of N1, N2, P3, and SW. For all analyses, the significance level was set at 0.05. Post-hoc testing of significant main effects was conducted using BONFERRONI method. Significant interactions were analyzed using simple-effect models. Results showed that the HTA group exhibited a enhanced N1 in comparison to the LTA group, F(2, 64) = 19.28, p < 0.01. And the interactions of the three factors was significant, F(1, 32) = 11.94, p<0.01. The interactions between picture and group was significant [Cz: F(1, 32) = 6.93, p<0.05, FCz: F(1, 32) = 5.22, p<0.05]; compared to LTA, HTA elicited different N1 amplitude between fearful and neutral images, with enhanced N1 to the fearful images. LTA elicited enhanced N2 compared with HTA, F(1, 32) = 4.83, p < 0.05. A significant relation between N2 and the trait score was found by using the stepwise regression analysis, F=6.97, p<0.05, R2=0.18. These results indicate that the HTA group allocated more attention resource to fearful images at the early emotional process stage (120~140 ms), whereas LTA group began to distinguish fearful from neutral at the later stage (230~250 ms). The executive function of inhibition might decrease with HTA, These results provide new evident to support the cognition-motivation model.
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