| Overweight and obesity are rapidly increasing in many countries around the world,and the World Health Organization identified obesity as a global epidemic in 1997.The number of overweight and obese individuals in China is also increasing rapidly.Our obese population surpassed the United States in 2014,ranking first in the world.The problem of children/adolescents with overweight/obesity in China is also becoming increasingly serious.The incidence of overweight/obesity in children/adolescents has increased rapidly from 5.3%in 1995 to 20.5%in 2014.A study by the Chinese Center for Disease Control and Prevention in 2019 found that the incidence of general obesity(body mass index,BMI?28kg/m~2)in Chinese adults was 14%,and the incidence of abdominal obesity(waist?90cm in men;waist?85cm in women)was 31.5%.Obesity increases the risk of physical and mental illness such as type 2 diabetes,hypertension,hyperlipidemia,coronary heart disease,cancer,gallbladder disease,and stroke,and even neurodegenerative diseases.Therefore,overweight and obesity have become one of the problems that the country needs to solve urgently.With the rise of cognitive psychology,more and more studies focus on the cognitive function of overweight or obese individuals.Inhibition control refers to individuals'ability to inhibit its own dominant response.The paper defines response control and conflict control as the two core components of inhibition control.Response control,which measures the behavioral inhibition of inhibition control,refers to inhibiting the dominance of external cue or automated response,to make a correct response to the target or the needs of the environment.Response control is usually measured using go/no-go tasks and stop signal tasks(SST).Conflict control measures the inhibition control at the cognitive level.When different representations appear at the same time and interfere with each other,cognitive conflicts occur.The brain monitors conflicts that occur during information processing,and its ability to respond differently to conflict information is conflict control.Conflict control is commonly measured with Stroop tasks,Flanker tasks,and Simon tasks.This paper mainly investigates whether the inhibition control in overweight individuals is weakened under the Chinese cultural background,the underlying neural mechanism of the inhibition control in overweight individuals,and how the spontaneous neural activity of the brain will affect the individuals'future dietary behavior and body composition.The paper contains three studies.Study 1explored the behavioral performance of inhibition control in adults with overweight.Study 2 explored the neuroelectrophysiological and blood oxygenation level dependent(BOLD)activities of inhibition control in individuals with overweight.Study 3 explored the predictive effects of brain activity on individuals'future eating behaviors and body composition.Study 1 consisted of two experiments.Experiment 1 explored the general response control in overweight individuals at the behavioral level by using a stop signal task.The results showed that the SSRT in overweight individuals was significantly longer than that in normal weight individuals,which indicated that the general response control in overweight individuals is poor.Experiment 2 adopted the classic color-word Stroop task to explore the general conflict control in overweight individuals at the behavior level.All participants were required to respond to the word and color respectively.The results showed that response times(RTs)to the word in overweight individuals were significantly slower than normal weight individuals under inconsistent trials.The finding suggested that the individuals'ability to resolve conflict information was firstly affected by overweight.Study 1 suggested that the inhibition control in overweight individuals showed a general decline at behavioral level.Study 2 consisted of four experiments.Experiment 3 used a food-specific go/no-go task combining with the event-related potentials(ERPs)to explore the neuroelectrophysiological activity of response control in individuals with overweight.This experiment involved two tasks:the food no-go task was to measure food-specific response control,and the flower no-go task was to measure general response control.No significant between-group differences were found in behavioral results.ERP results showed that P2 amplitudes in individuals with overweight were greater than those in normal weight individuals in the early processing stages.During the conflict monitoring phase,there were reductions of N2a and N2b amplitudes in overweight individuals.During the inhibition phase,enhanced P3 amplitudes were found in overweight individuals.The findings indicated that overweight individuals have early attentional bias towards food stimuli,and their ability to monitor conflicts is decreased,and more cognitive resources need to be recruited to food-specific stimuli.Experiment 3 was failed to find significant differences between groups in behavioral level.We thought it may be due to the difficulty of the task used in experiment 3 was too easy to result in ceiling effect.Therefore,we modified the go/no-go task by adding working memory requirement to the classic go/no-go task in experiment 4.The modified go/no-go task with functional magnetic resonance imaging(fMRI)was adopted to explore the BOLD activity of response control in overweight individuals.Behavioral results showed that the accuracy of low-calorie foods in overweight individuals was significantly lower than that in normal weight individuals.The fMRI results showed that the deactivation of the right caudate in overweight individuals was significantly smaller than that in normal weight individuals,and the activation of the right middle temporal gyrus in overweight individuals was significantly weaker than that in normal weight individuals.The Pearson correlation analysis of the beta value in the right caudate nucleus and the right middle temporal gyrus with body mass index(BMI),waist-hip ratio,and body fat ratio showed that the right caudate in high-calorie no-go trials was significantly positively correlated with BMI and body fat rate,and the right caudate in low-calorie no-go trials was only significantly positively correlated with body fat rate.The right middle temporal gyrus in high-calorie no-go trials had a significantly negative correlation with waist-hip ratio,and the right middle temporal gyrus in low-calorie no-go trials had a significantly negative correlation with BMI and body fat rate.This indicated that the reduction of food-specific response control may be one of the main factors for overweight or obesity,and the right caudate nucleus and the right middle temporal gyrus may be potential brain mechanisms for the reduction of food-specific response control in overweight individuals.Experiment 5 employed a newly-designed food specific conflict task to explore the neuroelectrophysiological activity of food specific conflict control in overweight individuals.The experimental stimulus was composed of food pictures and calorie information,and was divided into consistent and inconsistent conditions,i.e.a combination of high-calorie food pictures with“high calories”is the consistent trial.Participants were required to respond to the consistency of the stimuli by pressing keys.Behavioral results showed that RTs in overweight individuals were significantly slower than those in normal weight individuals.ERP results showed that N2 and N450 amplitudes in overweight individuals were significantly smaller than those in normal weight individuals,but P3 and LPC amplitudes in overweight individuals were significantly greater than those in normal weight individuals.These showed that the ability to monitor and resolve conflict information was decreased in overweight individuals.In addition,overweight individuals recruited more cognitive resources to food-specific stimuli,and tend to have higher-order processing of food-related stimuli involving motivation or emotion.The experiment explored the conflict control in overweight individuals from the perspective of dynamic changes,which provided new ideas and perspectives for future research.Based on the food-specific conflict task used in experiment 5,we further adapted it to a food-specific Stroop task in experiment 6.The experimental stimulus also consisted of food pictures and calorie information,and the center of food pictures was covered with calorie information.The combination of stimuli was divided into consistent and inconsistent conditions.For example,writing“high calories”on high-calorie foods was a consistent condition.Participants were required to respond to food pictures and calorie information separately by pressing keys.When participants responded to food pictures,the influence of calorie information was ignored.Likewise,they needed to ignore the effect of the food pictures when participants responded to the calorie information.Behavioral results showed that when responding to food pictures and calorie information,the RTs of overweight individuals were significantly slower than those of normal weight individuals.There were no significant differences between groups in accuracy.The fMRI results showed that when responding to food pictures,compared with the consistent trials,the larger right inferior frontal gyrus(IFG)was activated in inconsistent trials.In addition,we have found the high-calorie foods specific inhibition,that is,a larger activation was found in the right middle frontal gyrus(MFG)under high-calorie foods inconsistent condition rather than the high-calorie foods consistent condition.In response to food pictures,no significant differences in brain regions were found between groups.When participants were required to respond to caloric information,the activation of bilateral angular gyrus in overweight individuals was reduced,compared to normal weight individuals.The underlying brain mechanism for the reduction of conflict control in overweight individuals is the angular gyrus.Study 3 consisted of two experiments.Experiment 7 investigated the predictive effect of spontaneous neural activity on the individuals'eating behavior in the future 7 days with the help of resting fMRI.After scanning the fMRI data,we used the empirical sampling method to investigate the eating behaviors of all participants in the future 7days,including food craving,resistance,choose to eat and food intake.All participants were surveyed 7 times every day.The results showed that the right superior frontal gyrus(SFG)could negatively predict the food intake in the future 7 days.Specifically,the stronger the spontaneous neural activity in the right superior frontal gyrus,the less the individuals will eat in the future 7 days.Experiment 8 also used the resting fMRI to investigate the predictive effect of spontaneous neural activity on the individuals'future body composition(BMI,waist-hip ratio,body fat rate,etc.).Six months after the fMRI data scan,we again invited all participants to the laboratory to measure their body composition.The results showed that the right superior frontal gyrus could predict the body fat rate of the individuals in the next six months,that is,the stronger the spontaneous neural activity in the right superior frontal gyrus,the lower the body fat rate of the individuals in the next six months.The right inferior temporal gyrus(ITG)could negatively predict the waist-to-hip ratio of individuals in the next six months,that is,the stronger the spontaneous neural activity in the right inferior temporal gyrus,the smaller individuals'waist-hip ratio.It shows that in the resting state,spontaneous neural activity of control-related brain regions can effectively predict the individuals'future eating behavior and body composition.A healthy lifestyle depends on the balance between impulsive and control systems,and the balance between dieting goals and weight control goals.Our research suggests that decreased control-related brain activity may play an important role in individuals'future diet management.This study defined response control and conflict control as the core components of inhibition control.The study newly designed a novel experimental task and used ERP and fMRI to separately investigate the neuroelectrophysiological and BOLD activities of the weakened inhibition control in overweight individuals,which not only aimed to examine the dynamic time course of inhibition control in overweight individuals,but also to examine their brain activation mode.In addition,the individuals'daily eating behavior and body composition were tracked,to explore the effect of spontaneous neural activity on the individuals'future eating behavior and body composition with the help of resting fMRI,which made the results more ecologically valid and realistic.Finally,the study provides empirical basis,neuroelectrophysiological and BOLD activities evidence for previous theoretical models.Furthermore,this study validates and extends previous theoretical models,and the theoretical model of the decreased inhibition control in overweight individuals was proposed,which promoted the development of the theories in this field.In summary,there is a general reduction in inhibition control in individuals with overweight.Greater P2,P3 and LPC amplitudes,and smaller N2(N2a and N2b)and N450 amplitudes were the neuroelectrophysiological markers of overweight individuals.The study about brain mechanism found a decrease in control-related brain activity,specifically manifested by smaller activation of the right middle temporal gyrus and bilateral angular gyrus in overweight individuals.Spontaneous neural activity in the right superior frontal gyrus and right inferior temporal gyrus can effectively predict the individuals'eating behavior and body composition in the future. |
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