| Objective:Panic disorder (PD) is a common mental disorder chara-cterized by recurrent, unexpected and sudden panic attacks. The mechanism underlying unexpected panic attacks has not yet been fully clarified. Neuropsychological studies have generally agreed that the abnormal processing of emotional information is one of the main features of panic disorder. The present study investigated the anomaly of pre-attentive processing in PD patients towards emotional faces.Rapid, non-conscious and involuntary information processing are considered as the main features of automaticity. It was speculated that the abnormal information processing may occur on automatic level according to the uncontrollable and unexpected attack. Previous behavioral and imaging studies did not reach a consensus for that. The mismatch negativity (MMN) component is an event-related potential (ERP) that reflects automatic change detection independent of subjects'attention, but it has not yet been fully applied to the study of panic disorder on automatic processing of emotional information. Emotional faces are ecologically stimuli that provide rich emotional information for interpersonal communication. In this study, we recorded expression-related visual mismatch negativity(vMMN) to explore the pre-attentive processing mechanism in PD patients towards to emotional faces and the specificitis of emotional valence with task-irrelevant emotional faces as effective media.Methods:17 patients with PD and 18 age-and sex-matched healthy volunteers during the same period were selected for the study. HAMA (14-item Hamilton Anxiety Rating Scale) and HRSD-17 (17-item Hamilton Rating Scale of Depression) were used to assess severity of anxiety and depression in subjects. Stimuli presented in the centre of screen consisted of two color schematic faces with neural, positive and negtive expressions in upright and inverted conditions. A visual oddball paradigm was used in the study. All subjects were instructed to count the green faces (targets) and ignore the red faces (non-targets). A 32 channel electroencephalogram was recorded. After off-line analysis, the mean amplitudes of vMMN elicited by red positive and negtive faces in bilateral posterior sites were extracted for statistics at time windows of 110-210 ms and 210-350 ms post-stimulus for individual subject. The two sub-components were analyzed using repeated measures analyses of variance (RMANOVAs).Results:1. The early vMMN and late vMMN elicited by emotional faces were significantly lower in PD patients than that in normal controls (ps<0.04). Additionally, the group difference was evident at only right hemisphere(but not left) in upright condition (p=0.003).2. More importantly, the differences of early and late vMMN between two groups were not significant in the stimulus condition of positive expression (ps>0.05), they reached significant level only for negative expression (ps<0.02).3. The amplitude of early vMMN was also significant decreased in PD patients compared with controls under the conditions of face inversion (p=0.008), which was not equally significant for late vMMN (p>0.05).Conclusion:1. There is an impairment of pre-attentive processing of emotional faces, which is significant at the right hemisphere.2. The specificity of the emotional valence is evident for the abnormal automatic processing of facial expression in PD patients, shown as impaired pre-attentive processing for negtive facial expression but normal for posi-tive expressions.3. In addition to the abnoamal automatic processing of emotional information, patients with PD may be accompanied by functional dysfun-ction of automatic processing for the low-level visual physical information. |
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