Dysfunction Of Preattentive Processing Of Auditory Information Among Patients With Generalized Anxiety Disorder: An Event-related Potential Study

Objective: Generalized anxiety disorder (GAD) is characterized by tension andexcessive worry on the day-to-day activities or events. Because GAD involves multipleorgans and has complex clinical presentation, most patients with GAD often see adoctor in the different clinical departments, consequently lagging of diagnosis andtreatment of the disease. We have not yet been fully illuminated the etiology andmechanism of generalized anxiety disorder. Neuropsychological studies suggest thatdysfunction of information processing is one of the main pathogenesis of generalizedanxiety disorder, and GAD patients exhibit dysfunction of information pre-attentiveprocessing.Event-related potentials (ERP) can be characterized of high temporal resolution andbe used to accurately reflect the dynamic process of cognitive processing. It couldregard as an ideal tool for recording the time course of information processing.Mismatch negativity (MMN) is an ERP component elicited without the attentioninvolved. It is defined by a negative deflection that elicited by infrequent stimuli(deviant) compared to the repeated stimuli (standard). It is a classicalelectrophysiological index reflecting automatic information processing. The purpose ofthe present study is to investigate whether pre-attentive processing of auditoryinformation among patients with GAD is impaired as measured by a multi-featureparadigm and to examine whether physical properties of sound are specific to generalized anxiety disorder.Method：20GAD patients and20gender-, age-and education-matched healthyvolunteers participated in this study. All patients fit criteria for generalized anxietydisorder in DSM-IV. Patients and normal healthy participants are required to completethe14-item Hamilton Anxiety Rating Scale (HAMA-14) and the17-item HamiltonRating Scale of Depression (HRSD-17). The multi-feature paradigm was used in thisstudy. Auditory stimuli contain standard stimulus and five deviants (sound frequency,intensity, duration, location, gap). Moreover, there are two levels in the frequency,intensity and location deviants. The each deviant stimulus is10%respectively andstandard stimulus is50%. In the process of experiment, subjects only watched silentmovies, neglecting auditory stimulus from headphones. After off-line analysis, thedifferent deviant amplitudes and latency of mismatch negativity were measured atcentral electrode(C3、Cz、C4) and frontal electrodes (F3、Fz、F4). Control group and0μV for each deviant type conducted with Three-factorial analyses of variance(ANOVAs) with repeated Measures, in order to determine whether the MMNamplitudes of control group significantly differ from zero. Mean amplitudes and latencywere subjected to three-way repeated-measures analysis of variance (ANOVA) withGAD group and control group. Relationship between the magnitudes of the MMN andHAMAscores were analyzed by Pearson correlations.Results：1.The main effect of group between five deviant MMN amplitudes of control groupand0μV was also significant, respectively for frequency(F（1，38）=26.731,p<0.001),intensity,(F（1，38）=71.368,p<0.001),duration(F（1，38）=6.422,p<0.05),location(F（1，38）=20.391,p<0.001), and gap(F（1，38）=4.253,p<0.05).2. The MMN amplitudes elicited by sound intensity (F(1,38)=4.647, p <0.05)weresignificantly reduced in GAD patients compared to the controls.3. The MMNs arising from the five deviants revealed a significant main effect ofregion, respectively for intensity(F(1,38)=75.580, p <0.01),frequency (F(1,38)=32.446,p <0.01),(F（1，38）=26.731,p<0.01), duration(F（1，38）=6.422,p=0.016), location(F(1,38) =45.789, p <0.01),and gap(F(1,38)=51.669, p <0.01),indicating frontal MMNamplitudes were significantly increased than the central area.4. The MMN amplitudes for five deviants had no correlation with HAMA score(p>0.05).Conclusion：1. GAD patients exhibited reduced automatic processing for auditory physicalinformation at pre-attentive stage.2. Impaired pre-attentive processing of intensity may be specific for GAD patients.3. Dysfunction of intensity pre-attentive processing in GAD patients had nocorrelation with severity of anxiety symptom.