No change in reward responsiveness, but decreased functional connectivity with right nucleus accumbens and left lateral occipital- precuneus cortex 3 months after sleeve gastrectomy

Abstract

Background: Obesity is known to be linked to nucleus accumbens activity and altered reward responsiveness. Sleeve gastrectomy (SG) is often used for treatment of morbid obesity and activity in the NAcc was shown to positively affect weight-loss at 12 months post-surgery. The aim of this study is to measure the change in reward responses and nucleus accumbens (NAcc) functional connectivity 3 months after SG. Methods: 25 patients with a diagnosis of obesity were evaluated pre-surgery and 3 months post-surgery with Snaith-Hamilton Pleasure Scale (SHAPS), Beck Depression Inventory (BDI) and body weight. As a laboratory-based measure of reward learning, they performed probabilistic reward task (PRT). Resting-state fMRI images were obtained from 7 participants pre and post surgery. Results: Both SHAPS, BDI and response bias and discriminability scores in PRT were not significantly different post-surgery. Mean percentage body weight loss of individuals were 20.07 %. Right NAcc functional connectivity with left lateral occipital- precuneus cortex decreased significantly post-surgery (105 voxels, voxel wise threshold p<0.05, FWE corrected), however no change in left NAcc connectivity was observed. Change in right NAcc functional connectivity was not correlated with weight loss. Conclusions: Previous literature on gambling and alcoholism showed increased NAcc-precuneus connectivity. Functional connectivity decrease between NAcc and precuneus in the resting state can be associated with reduced impulsivity and sensation-seeking observed after BS which correlates positively with successful weight loss.