A Study On The Correlation Between Food Evaluation And Reward Sensitivity

Nowadays obesity has become a great threat to human beings’ health with abundant supplement of food immoderate diet. Ubiquitous obesity ranked third of people’s health threat following cardiovascular diseases and cancer. Obesity can lead to cardiovascular and cerebrovascular diseases, diabetes, cholecystitis, beside this, it is closely related to a series social and psychology problems such as self-abasement.The causes of obesity are complicated, it is reported that genetics, side effect of drugs,and dietary behavior may result in obesity. From view of psychology, we focused on dietary behavior of obese people.Dietary behavior is not just eating, it contains relevant factors such as knowledge about nutrition, diet belief and attitude, lifestyle, emotional state, cultural tradition,value and so on. In addition, in the process of eating, whether food preference or not further has impact on the behavior of eating, that is, the reward resulted from eating is also an important factor that influences diet behavior.It is reported that reward system functional disorder can lead to pathological diet behavior. The reward system can only provide evolutional function when food supply is insufficient, as a result, this system requires energy restore and consumption to achieve hemostasis. On the contrary, in circumstances of sufficient food, when the food acquisition cost is low, the reward system may lead to high risk of ill-health, for example, obesity. It is widely accepted that orbitofrontal cortex(OFC) and amygdala play significant role in environment cues and food evaluation process. The function of orbitofrontal cortex and amygdala are closely related, to improve the reward system orbitofrontal cortex, amygdala, striatum, midbrain, and anterior cingutate, contribute to this process. A widely recognized hypothesis that amygdala influences the direct relationship of stimulation and evaluation by guiding information input of OFC, and in consequence, the information further influences the output of reward evaluation. But,the processing mechanism how amygdala and OFC influence reward system is still undiscovered. According to current research progress in this field, we learned the relationship of reward sensitivity and brain activity in food evaluation process betweennormal weight people and over-weight people in this research.This research consists of two parts, research 1 using questionnaire and research 2using fMRI. Research 1 surveyed the possible difference on reward sensitivity between the experimental group participates(over-weight participates) and control participates(normal-weight participates) using Reward sensitivity subscales of SPSRQ questionnaire. Research 2 tested three aspects using fMRI: 1) when given food pictures and asked to rate on food pictures(4 levels evaluation), if there’s difference in brain activity between the experimental group participates(over-weight participates) and control participates(normal-weight participates) in the fMRI scanning process; 2)tested the relationship of reward sensitivity and brain activity stimulation among all participates, experimental participates and control participates using reward sensitivity of participates as concomitant variable; 3) tested the relationship of region of interest(ROI) and reward sensitivity between experimental participates and control participates, using reward sensitivity value of participates as independent variable, and orbitofrontal cortex recognized as ROI, extracted beta value as dependent variable.Based on the female college students as the research object, using nuclear magnetic resonance(NMR) method, questionnaire method, attempts to study the relationship between food sensitivity evaluation and reward: 1) the reward sensitivity scores; 2) overweight and normal weight. This study recruited 41 female college students as subjects, with four people are eliminated because they do not conform to the requirements of the experiments, a total of 37 data are analyzed. 37 people, 20 people as experimental group, namely overweight; 17 other people as control group,the normal weight. Before MRI scan, all participants were between four to six hours without eating, nor drink any caffeinated drinks, such as tea, coffee and so on. After an MRI scan, the participants filled out the reward sensitivity questionnaire. Research results show that: 1) in the face of high quantity of heat food and in the face of low calorie food pictures, overweight individuals than normal weight individuals more strongly activated bilateral taste cortex, including mOFC, ACC and PCC; 2) all of the participants in the face of high quantity of heat food pictures than facing low calorie food pictures, more strongly activated the orbitofrontal cortex, center orbitofrontal cortex and the anterior cingulate and Precuneus. Activation is related to rewardsensitivity. 3) tested the relationship of region of interest(ROI) and reward sensitivity between experimental participates and control participates, using reward sensitivity value of participates as independent variable, and orbitofrontal cortex recognized as ROI, extracted beta value as dependent variable. The activation of OFC is positive correlated to reward sensitivity when evaluated high-calorie pictures, and negative correlated to reward sensitivity when evaluated low-calorie pictures.