Objective: Neuronal circuits involved in the pathophysiology of anxiety are not yet fully understood. We used functional connectivity MRI to explore the characteristic of functional connectivity in anxiety disorders patient and the neural mechanism of this disease. This work was selected as an oral presentation in 2006 ISMRM.
Methods: Twenty right-handed subjects were included in this study, and were divided into two groups. The anxiety (P) group (n = 10; 7 male, mean age 42 years) consisted of patients meeting DSM-IV criteria for a principal diagnosis of anxiety disorder. The control (C) group consisted of volunteers free of psychiatric symptoms, and was matched on age and gender (n = 10; 7 male) with the panic patients. The subjects underwent noninvasive functional magnetic resonance imaging while listening actively to (1): emotionally neutral word alternating with no word as the control condition (CN, PN), and (2): threat-related words alternating with emotionally neutral word as the experimental condition (CT, PT). Each word was presented in pseudorandom order in each 16 s block of 12 words of the same type. Eight alternating blocks of neutral words were presented for about 256 s. The subject was only asked to passively listen to each word. All MRI data were obtained on a 1.5-Tesla scanner Data analysis was performed with SPM99 to find significant activations in two tasks for two groups. Based on group t-test, we chose two anatomically defined regions: left superior temporal gyrus (GTs) and right GTs. Then, based on individual t-map, the voxel with the largest t-value within two regions was taken as the subject-specific peak voxel. We define clusters based on faces and edges, but not corners, so each voxel has 18 neighbors. Subject-specific averaged time series were extracted by averaging the time series of 19 voxels. Since healthy control subjects showed no significant activation (corrected, P < 0.05) during processing of anxiety word to neutral word, region of interest during processing of neutral word to no word was used as substitution. The connectivity degree eta(i j) between the node i and the node j is used to identify the change of the functional connectivity associated with differential tasks, which calculated by using the methods that have developed by ourselves. Moreover, we just consider coherence in low-frequency (0-0.15 Hz).
Results: The activation brain regions have been reported in our previous work. Patients were significant different from normal controls on two experiments. The connectivity degree of left Gts and right Gts in two tasks across all subjects was calculated. Comparing during processing neutral word to blank, a significant decrease (P < 0.001) in functional degree was observed during processing of threaten word to neutral word (eta = 0.5636 for CN, eta = 0.555 for CT, eta = 0.5616 for PN, eta = 0.4926 for PT). Especially, the greater decrease connectivity degree was identified for patient group compared with normal control during threat-related words alternating with emotionally neutral word condition. The connectivity degree identifies that functional interactions change with differential task.
Conclusion: This result suggests decreased functional connectivity among left superior temporal gyrus and right GTs during processing of anxiety word to neutral word in anxiety patients. This dysfunction may mediate the neural mechanism of this sort of disease.