Pre-attentional Processing Of Facial Expressions Among Patients With Generalized Anxiety Disorder: An Event-related Potential Study

Objective: The main features of generalized anxiety disorder is shownas excessive uncontrollable worry and tension accompanied by autonomic nervoussymptoms or movement of disturbed symptoms. With the high prevalence,thegeneralized anxiety disorder, has become one of the serious diseases endangeringhuman health.In spite of the pathogenesis of GAD is unknown,most clinicalobservations and experimental evidence proposed that the abnormality of processemotional information was associated with the aetiology of generalized anxietydisorder.Other people’s facial expression convey socially important information,quicklyidentifing the threatening and nonthreatening facial expressions of great significance forthe surivival of manking. Given that the clinical characteristics of generalized anxietydisorder patients, it suggested that the abnormal processing of emotional informationmost likely occur in automatic stage. At present,there are few researchs on automaticinformation processing stage (especially pre-attentional processing) of patients withgeneralized anxiety disorder. The preceding processing of attention is called aspre-attention. Pre-attentive processing is an unconscious processing of information fromthe environment to determine what is important and should be noticed. The pre-attentiveprocessing reflected the ability of automatic change-detection of our brains. Pre-attention is always out of consciousness. Because of the limitations of thetraditional behavioral method.,it is difficult to study pre-attentive processing.Event-related brain potential (ERP) has a unique advantage on cognitive domain. It is anon-invasive method to measures brain activity and accurately record the time course ofemotional information. Mismatch negativity (MMN) is the main biological index ofpre-attentive processing. MMN obtained from the difference ERP waveform fromdeviant and standard stimuli of the classic oddball paradigm. Visual MMN(vMMN) thatevoked from facial expressions is known as expression-related Visual MMN(EMMN).It reflects the pre-attentive processing of facial expressions, it can be used forprobe the physiological mechanism of patients with GAD.Methods:20patients with generalized anxiety disorder accord with DSM-IV and20healthy volunteers participants were selected to match with age,gender and educationin the current study. In order to evaluate the severity of anxiety and depression,all of thesubjects must finish the HAMA and HRSD-17. The stimuli consisted of the trueperson’s faces, including two negative facial emotions.Select fear faces as threateningand sad faces as non-threatening stimuli. The Reverse-oddball paradigm was used in ourexperiment. All participants were demanded to count the cross (targets) and ignore thefaces (non-targets). Electroencephalogram (EEG) was continuously recorded that used a64-channel electrode cap to recorded and analyzed. Analysis the mean amplitudes ofEMMN elicited by different facial emotions in the parietal(p7/p8) and occipital(o1/o2)electrodes.The mean amplitudes of MMNs were analyzed by repeated measurementanalysis.Results:1.There had no difference on EMMN amplitudes of fearful expression (threatening)in participats with generalized anxiety disorder compared to those in healthycontrols(p>0.05).2.There was a significant main effect of group for EMMN amplitudes evoked bysad ones (nonthreatening), the amplitudes were significantly decreased in patients withGAD than the controls(p<0.05).3.There was no remarkable relevance between EMMN amplitudes and HAMA orHAMD-17score(p>0.05). Conclusion:1.It implied that the pre-attentional processing of patients with generalized anxietydisorder was impaired for nonthreatening expressions (sad) but not threatening ones(fear).2.No correlation was found between abnormal emotional information processing ofgeneralized anxiety disorder and anxiety and the severity of depression.