661 The Resting and Guided Thinking State Functional Connectivity of the Nausea Network in Cyclic Vomiting Syndrome: The Effect of Emotional Stress

Abstract

BACKGROUND: Cyclic vomiting syndrome (CVS) is characterized by episodic nausea and vomiting and is often triggered by several factors including emotional stress. With the recent description of neural correlates of nausea (Napadow et al. Cerebral Cortex, 2012) it is now possible to directly study its role in CVS patients. Our AIM was to determine and compare the effect of emotional stress on the resting state functional connectivity of the nausea network between patients with CVS and healthy controls (HC). METHODS: We used guided thinking state fMRI to study the effect of emotional stress on 10 Rome III positive CSV patients (6F, ages 19-49, average length of disease 11 years) in their inter-episodic phase and 10 HC (6F, ages 21-54). Guided thinking state fMRI is an emerging concept where a prior task or induced mood is used to modulate resting state networks. Functional MRI data was acquired during two 10-minute resting state scans (TR 2 s, 3.5 mm isotropic voxels, 64x64 matrix, 240 mm FOV, 3.5 mm slice thickness and 41 contiguous slices) using a 3T MRI scanner with a 32-channel head coil, before and after volunteers were shown 3 minutes of pictures with a negative valence from a standardized picture database. We used Analysis of Functional Neuroimages software and the afni_proc.py python script for analysis. Fourteen four-millimeter radius seeds were dropped using coordinates defined a priori as the nausea network. The average time series were extracted from the seed regions and the Pearson cross correlation coefficient (CC) was calculated to assess the functional connectivity of each of these seeds to the other seeds within the network. Unpaired t-tests were used for comparison and false discovery rate (FDR) was utilized to correct for multiple comparisons. RESULTS: There was no difference in the connectivity of the nausea network between the CVS patients and HC prior to emotional stress. However, after emotional stress there were significant differences observed between the two groups in connections between the right (R) premotor area (PM) and R middle cingulate cortex (MCC) and between the R superior temporal gyrus (STG) and R perigenual anterior cingulate cortex (pgACC) (FIgures 1, 2). In addition, HC but not CVS patients exhibited alterations of the nausea network following emotional stress between the R secondary somatosensory area and the R MCC and between the R PM and R pgACC. CONCLUSIONS: There are significant differences in the functional connectivity of the nausea network between CVS patients and HC following emotional stress. This finding contributes to our understanding of the role of emotional stress in CVS.