The Cognitive And Neural Mechanisms Of Reward Processing Superiority For Disinhibited Eaters

Eating is the most basic physiological need of human beings.With the development of social economy,the problems of eating disorders and overweight and obesity are becoming more and more serious in China.According to the data published in Lancet and WHO,the obese population in China has surpassed that in the United States,ranking first in the world,and the proportion of overweight and obesity in the total population in China has surpassed that in neighboring Japan and Korea.When modern media associates beauty with "bone feeling",fear of obesity has become a common concern of women.Ironically,the overwhelming majority of individuals who exercise eating control tend to gain weight in the end.Individuals tend to have "weight loss-rebound-weight loss-rebound" type of fluctuation in weight,weight cycle like the track of yo-yo,known as the "yo-yo effect".Theory and research have shown that disinhibited eating is an important eating behavioral trait and a key risk factor for success or failure of eating control.Disinhibited eating refers to the tendency to habitually overeating in the absence of physical hunger when facing emotional distress or external food temptation cues.Disinhibition is an opportunistic eating trait,which can be generally understood as inhibition relief or disengagement from eating control.Disinhibition trait are accompanied by increased attention bias and hedonic response to food cues.Therefore,a systematic study on the characteristics of disinhibited eating will not only enrich and expand the relevant theory of eating control,but also help to carry out the practical application of intervention and prevention of eating disorders and obesity.Previous studies on the food reward and hedonic processing of disinhibited eaters have some weaknesses.Previous studies on disinhibited eating were mostly based on questionnaires survey or the effects of itself on body weight.There were few studies using more objective behavioral experimental paradigm and exploring its neurological mechanism.If no studies have been conducted to investigate the reward-anticipated sensitivity to food cues in disinhibited eaters.In addition,the goal conflict model considers that the individual's dietary behavior is affected by two incompatible goals: eating enjoyment and weight control.However,the model does not explain what motivation individuals pursue for weight control are more specific.It has been pointed out that there are two more specific potential motivations for individuals to pursue weight control: thin figure drive and health drive.Based on the previous research in the field of thin body image and our previous survey among young female college students,we believe that the primary motivation for young women to control their eating is not health considerations but the pursuit of thin body.Therefore,young women's dietary behavior should be influenced by two incompatible motivations: eating enjoyment and thin figure.However,there is no suitable experimental paradigm to directly assess the conflict processing between the two motivations.Therefore,based on the expanded understanding of goal conflict model,this study focuses on the key factor of inhibition relief in eating control-"food reward and hedonic processing".From the perspectives of explicit reward anticipation,implicit preference,dual-drive interference superiority and resting brain mechanism,the cognitive and neurological mechanisms of reward processing superiority for disinhibited eaters will be systematically studied.In the first study,we used amended food incentive delay task to examine the characteristics of reward-anticipated sensitivity for healthy and unhealthy foods in disinhibited eater at the explicit level.In behavioral response time(experiment 1),there was no significant difference in the sensitivity to reward anticipation between healthy and unhealthy foods.This result is consistent with the behavioral results of previous studies with incentive delay task.This suggests that disinhibited eaters may be able to consciously regulate their behavioral response patterns on explicit behavior.But they gave a more "honest" answer on the neuronal activation of reward system areas(experiment 2).In the process of comparing reward anticipation of delicious unhealthy food with healthy food,the higher the level of disinhibited eating,individual had higher activation of subcortical dopamine reward system areas(dorsal striatum and thalamus).In the comparison of reward feedback processing,the higher level of disinhibited eating,individual had higher activation of the anterior insula,which is responsible for gustatory representation and interoceptive processing.In the second study,the implicit reward preference for delicious food cues in disinhibited eaters were investigated.In experiment 3,a single-category implicit association test incorporating positive and negative emotional pictures was used.It was found that there was a stronger implicit preference for delicious food cues in disinhibited eaters.Experiments 4 using pictorial affective priming task also found that disinhibited eaters had stronger implicit positive emotional bonds to delicious foods.This suggests that disinhibited eaters unconsciously were more sensitive to delicious food cues and had stronger activation of "hot" reward representations.In study 3,by integrating food and body stimuli,we designed a novel double-driven interference task to evaluate the conflict interference effects between high-calorie delicious food cues and lean body and its neuromechanisms.In experiment 5,we found that in food-driven and figure-driven dual-driven conflict processing,disinhibited eaters showed stronger interference effect in the context of food reward.This indicates that the disinhibited eaters are more sensitive to the background of food reward and may have stronger automatic attention bias to the interference of food reward.In experiment 6,we found that the higher the level of disinhibited eating trait,individuals had higher activation in the emotional reward memory processing regions(right parahippocampal gyrus and middle temporal gyrus)and taste processing region(right posterior central gyrus)in comparison with the interference effect of food background and body background.Psychophysiological interaction analysis(PPI)found that the higher level of disinhibited eating,individuals had stronger the functional connectivity between the parahippocampal gyrus and the left middle temporal gyrus.The results showed that the interference of food reward was stronger,and the motivation of food reward enjoyment was stronger in disinhibited eaters.The background of food reward disturbance may activate the pleasure reward memory and taste experience brought by eating food in the past.Study 4 explored the resting brain mechanism of reward processing superiority in disinhibited eaters.Experiments 7 examined the characteristics of local brain coherence(ReHo,Regional Homogeneit)and resting-state functional connectivity(RSFC)in disinhibited eaters,and their relationship with trait food craving.Disinhibited eaters showed higher spontaneous activity in the orbitofrontal cortex and the parahippocampal gyrus,which were positively correlated with food craving.At the same time,functional connectivity between the orbitofrontal cortex and the body image self-referencing processing area(precuneus)was reduced.In the more stable resting-state spontaneous activity,it reflected that the reward hedonic motivation in daily life is stronger for disinhibited eaters,while the self-reflection processing function is weakened.So,it is easier to forget their body pursuit of goals and then the disengage the individual inhibition goal and loss of control eating occurred.To sum up,this study systematically explored the cognitive and neurological mechanisms of "food reward hedonic processing" in disinhibited eaters and expanded the goal conflict model.When confronted with the anticipation cue of delicious food reward expectation,the high disinhibited individuals formed stronger anticipation cue-reward reinforcement motivation reflex,which was reflected in the stronger activation in the basal-thalamic reward system.When food reward feedback arrived,high disinhibited individuals had stronger activation response in the anterior insula that was responsible for taste representation and interoceptive processing.This may indicate that disinhibited eaters pay more attention to the sensory enjoyment brought about by food rewards.Increased implicit preference for food reward cues indicates that the "hot" channel of eating enjoyment is more easily activated when disinhibited eaters facing external food temptation.When confronted with the conflict between hedonic-driven and figure-driven drives,disinhibited eaters were more sensitive to the food-conflicting background.The interference effect of food background is greater than that of weight background.Moreover,high disinhibited individuals had stronger activation in emotional reward memory and taste perception processing areas.In conclusion,the increased reward anticipation and implicit preferences for delicious food cues lead to the breakdown of the balance between the eating enjoyment strength and thin figure-driven goal.The resting brain mechanism also supports the imbalance.Enhanced enjoyment motivation of food reward and weakened cognitive representation of thin figure goal make it easier for disinhibited eaters to abandon their healthy diet planning,so they have a higher probability of uncontrolled eating,which leads to overweight,obesity and bulimia.The main innovations of this study are as follows: first,we expanded the goal conflict model in young women;second,we designed a double-driven interference task to evaluate the conflict processing between eating enjoyment and thin figure goal;we used single-category implicit association test and pictorial affective priming task to investigate the implicit reward preference in disinhibited eaters..