The Cognitive And Brain Mechanism Of Children's Food Reward Anticipation

In China,the rate of children with overweight and obesity has been increasing over the recent years.If one is overweight or obese in his/her childhood,there would be a higher risk of obesity for him/her after becoming an adult.So one of the most important things for us is to pay attention to and try to solve the obesity problem in children.Obviously,the food environment may be an important factor affecting children's dietary behaviors and weight gain.People who are obese or overweight are often accompanied by the characteristics of high food responsiveness,which is manifested by frequent eating or excessive consumption.Individuals with such kind of eating behavioral style are always more responsive to food cues,thus leading to increased food intake,abnormal dietary patterns and obesity.So the food responsiveness becomes a key variable we need to focus on.In our daily life,there are many cues that are paired with direct food reward for many times.When individuals have acquired the cue-reward association,they just become physiologically and mentally responsive to these cues.A series of studies in the past have also confirmed that individuals' responses to food cues are closely related to their health.For example,activities in these specific brain areas predicts subject's future food choices,food intake and weight gain.Therefore,it is necessary to explore the effect and potential mechanism of reward anticipation in different groups(such as healthy children).The objective of our study was to explore the cognitive and brain mechanisms of the processing of food reward anticipation in children as well as the role food responsiveness plays in it.We hypothesized that children with high food responsiveness might have stronger associative learning ability related to food reward,and children with high food responsiveness would also have enhanced activity in reward-related brain areas and stronger connectivity between those areas when exposed to conditioned neutral cues.In order to test these hypotheses,in Study 1,based on the Incentive Sensitization theory and Pavlov's classical conditioning,the appetite reversal learning task was used to evaluate children's associative learning ability related to food reward.Fifty children's parents filled in the Children's Eating Behaviour Questionnaire(CEBQ).However,there was no significant correlation between food responsiveness score and associative learning ability(including both acquisition and reversal).In Study 2,twenty-nine children participated in this experiment and their parents filled in the same questionnaire.The food reward anticipation task was used,combined with f MRI technique,to explore the brain activation pattern of children in response to conditioned neutral cues.The results showed that the fusiform gyrus,lateral orbitofrontal cortex(LOFC),insula,amygdala,putamen and caudate nucleus were all activated when children were exposed to food image reward.And the activation in the brain area(bilateral nucleus accumbens)related to reward anticipation was observed when children were exposed to food cues symbolizing reward,and activity in the nucleus accumbens(NAc)has a significant positive correlation with children's food responsiveness.Based on this,we conducted the psychophysiological interaction(PPI)analysis with bilateral nucleus accumbens chosen as the seed region,and we found functional connection between NAc and ventral tegmental area(VTA)and one between NAc and habenula(Hb).These connections were also regulated by food responsiveness.To be specific,higher connectivity of NAc-VTA and NAc-Hb were correlated with children's higher food responsiveness when they were exposed to food cues.The dynamic causal modeling(DCM)analysis was also used to establish brain activity pattern among NAc,VTA and Hb in the processing of food reward anticipation and explore the causality among activities in the three regions.Our results showed that there were two parallel causal pathways from VTA to NAc and Hb,which are related to cue anticipation.In conclusion,our results partly supported our hypotheses.The key brain regions implicated in food reward or reward anticipation(including the fusiform gyrus,lateral orbitofrontal cortex,insula,amygdala,putamen,caudate and nucleus accumbens)were all activated by the food reward anticipation task,which showed validity of our adapted task.And other results might indicate that children's food responsiveness doesn't affect their ability of cue-reward associative learning.But this variable might influence children's brain reactivity to food cues and lead to changes of the connectivity between brain regions in the processing of food reward anticipation,thus resulting in subsequent increased food consumption and obesity.This effect of cues was found because that cues might obtain the motivational properties,namely incentive salience,through associative learning and then become attractive.Our results partly supported the incentive sensitization theory and provided further supplement and support for the theoretical research in the field of children's obesity and eating behavior.Since children are in a period of rapid physical and mental development,which is also a critical period for the develop of food responsiveness and eating habits,we can also explore the prediction effect of food responsiveness on future eating behavior and weight changes in children to further supplement and support our conclusions.