The FMRI Study Of Emotional Processing Network In Generalized Anxiety Disorder

Generalized anxiety disorder’s(GAD’s)key symptom is excessive,uncontrollable,sustained worry.Studies found that GAD had a lifetime prevalence and 12-month prevalence of 5.7%,3.1%respectively,with high disability rate and showing a significant degree of disability,which brought individual’s normal life a considerable impact.However,the efficacy of treatment for GAD remained to be poor and the pathological basis of GAD remained largely unknown.GAD was found to be highly associated with emotional dysregulation.fMRI-based studies have not only found that GAD patients exhibited abnormalities in some brain regions under emotion task,but also found that these "abnormal regions" in GAD patients centered in prefrontal cortex(PFC)and limbic area.However,in the pursuit of exploring GAD’s neurobiological basis,extant studies have mainly been conducted in the perspective of brain regions’own function and functional connectivity between brain regions,it remained largely unclear that to what extent and in which way the GAD patients would be abnormal in terms of brain network,relative to healthy controls.This study aimed to address this question.The current study employed case control design.According to corresponding criteria,this study recruited 42 participants in total,of them,23 were GAD patients,19 were healthy controls(HCs).Task-related fMRI was used in this study,which required participants to finish a block-designed emotion identification task during scanning.The whole study included two parts:the first part compared the brain activation between GAD patients and HCs under positive and negative condition;based on the first part and previous results concerning GAD,the second part selected some number of regions of interest(ROI)and separately modeled emotion processing network for GAD group and HC group.The interpretations for results in the second part were in terms of hub,global connectivity and connection density.The main results were following:The first part:(1)under positive condition,comparing to HCs,the activity-increased brain regions in GAD patients included:right postcentral gyrus(t=3.02,p<0.05),right superior temporal gyrus(t=3.86,p<0.05),right caudate(t=4.02,p<0.05);the activity-decreased brain regions in GAD patients included:right superior frontal gyrus(t=3.11,p<0.05),right medial frontal gyrus(t=4.01,p<0.05),left middle frontal gyrus(t=2.69,p<0.05),left insula(t=3.08,p<0.05),left anterior cingulate cortex(t=2.38,p<0.05),left hippocampus(t=3.48,p<0.05)and so on.(2)Under negative condition,comparing to HCs,the activity-increased brain regions in GAD patients included:right inferior frontal gyrus(t=3.19,p<0.05);the activity-decreased brain regions in GAD patients included:right superior frontal gyrus(t=3.87,p<0.05),left superior frontal gyrus(t-4.05,p<0.05),left middle frontal gyrus(t=2.78,p<0.05),left anterior cingulate cortex(t=2.64,p<0.05),right anterior cingulate cortex(t=3.60,p<0.05)and so on.The second part:both groups had connection LACC-LMFG(Left Anterior Cingulate Cortex-Left Medial Frontal Gyrus)and connection LSFG-RSFG(Left Superior Frontal Gyrus-Right Superior Frontal Gyrus)under negative or positive condition.From the perspective of PFC subnetwork:LACC was the hub under negative and positive condition in HC group,while LMFG was the hub under positive condition and LACC,LMFG,RSFG were hubs under negative condition in GAD group.From the perspective of limbic subnetwork:left amygdala(LAmygdala)was the hub under negative and positive condition in HC group,while right insula(RInsula)was the hub under positive condition and RInsula,RParah(Right Parahippocampus)were hubs under negative condition.From the perspective of the connection between PFC subnetwork and limbic subnetwork:under positive condition,2 connections were found in HC group,which were respectively LACC-LAmygdala and LSFG-LParah,While only 1 connection was found in GAD group,which was LMFG-RInsula;under negative condition,1 connection was found in HC group,which was LACC-LAmygdala,while 3 connections were found in GAD group,which were respectively LACC-RInsula,LMFG-RParah,RSFG-LAmygdala.From the perspective of connection density:under positive condition,lower connection density was found in GAD group(7 connections)than that in HC group(8 connections);under negative condition,higher connection density was found in GAD group(10 connections)than that in HC group(7 connections).From the perspective of global connectivity:under positive condition,both top-down and bottom-up connection were found in HC group,while only bottom-up connection was found in GAD group;under negative condition,top-down connection was found in HC group,while only bottom-up connection was found in GAD group.In conclusion,the brain regions that showed abnormal activation were mainly in the PFC and limbic area and most of them showed hypoactivity.The abnormalities in the emotion processing network of GAD patients included:the malfunction of the insula and the amygdala,lack of top-down control,disruption between the amygdala and the PFC subnetwork,highly interconnected in the network under negative condition.