Altered Effective Connectivity Of The Insula In Nicotine Addiction

Objective The purpose of this study was to investigate the changes of effectiveconnectivity associated with insular in different nicotine addiction sessions, in order tounderstand the role of insula in addiction and its function.Methods Twenty smokers were scanned resting-state functional magnetic resonanceimaging in two sessions of different conditions: smoking abstinence followed by smokingsatiety. The imaging data were acquired using GE Signa HDx1.5T MRI scanner with an8-channel standard phased array head coil. During the6-min resting scan, participants wereinstructed to simply relax with closed eyes and remain awake. The High-resolutionT1-weighted anatomical images using a3D fast spoiled gradient-recalled （FSPGR）sequence as follows:1.0mm slice thickness, TR=8.8ms, TE=2.8ms, FA=20°, matrixsize=256×256, FOV=240mm2, no gap.30slices covered the whole brain aligned along theAC-PC line. Bold functional images were acquired in the same relative slice locations using agradient-recalled echo planar imaging（EPI）sequences: TR=2000ms, TE=30ms, FA=60°,matrix size=64×64, FOV=240mm2, slice thickness/gap=4.0mm/0mm. A total of180volumes were collected, resulting in a total scan time of360s.Group ICA was firstly adopted to obtain the independent component patterns, A pairedt-test on ICA spatial patterns revealed regions of interest such as the insula,parahippocampus, precuneus, dorsal anterior cingulate cortex, rostral anterior cingulate cortex,supplementary motor area and ventromedial/dorsolateral prefrontal cortex, and the effectiveconnectivity from insula to other regions was investigated subsequently using GCA.Results Group results of independent components. Shown are global networks, whichshow high similarity to activated addictive areas. the dorsal anterior cingulate cortex andsupplementary motor area. the precuneus and rostral anterior cingulate cortex, parahippocampus, the insular and ventromedial prefrontal cortex.Eight ROIs in total located in the following brain regions: the insular, dACC, dlPFC,vmPFC, SMA, rACC, precuneus and parahippocampus.In smoking abstinence, the insulashowed the increased effective connectivity with dorsolateral prefrontal cortex, ventromedialprefrontal cortex, dorsal anterior cingulate cortex, rostral anterior cingulate cortex, precuneus;while in smoking satiety, there is no significant changes for effective connectivity. Referringto the out-in degree metrics, the out-in degree of insular is+2in smoking abstinence, whereasin satiety condition is0.Conclusion Insula is a signal output node in smoking abstinence, with its interoceptivefunction monitoring the change of physiological state of the body when in smokingabstinence, and then integrating the each brain activity to produce subjective consciousnessso an to facilitate addiction.