Impulsivity And Neural Mechanisms In Overweight/obese Individuals

Nowadays,how to treat overweight and obese people who have an excessive diet has become one of the world's public health problems due to the sharp increase in the trend of overweight and obesity.Impulsivity is a multi-dimensional and multi-component structure that is considered to be an important factor in obesity.Studies have shown that overweight and obese individuals are more likely to exhibit impulsivity than normal weight individuals.They not only have the poorer ability to delay the satisfaction,but also have difficulty in inhibiting the dominant response,and the weight is more likely to rebound.The aim of this study was to elucidate the performance of overweight and obese people in two main aspects of food impulsivity(decision impulsivity and action impulsivity),combined with behavioral experiments and functional magnetic resonance imaging techniques to investigate the delayed discount and response inhibition ability and its neural mechanism in the food background.In study one,we aimed to investigate how overweight/obese people represent the immediate and delayed reward during intertemporal choice.A total of 79 college students were recruited,including 33 overweight/obese and 46 control subjects.We dependently manipulate the magnitude of immediate and delayed rewards combined with event-related fMRI design to measure the human brain activity.The independent sample T test showed a significant difference in the percentage of delay between the overweight/obese and the control group.In easy conditions,the results indicated that lower activations in overweight/obese individuals was found in response to the trial of S>L compared to normal individuals in anterior cingulate cortex,frontal lobes and occipital lobe;in the trial of L>S,the activation of brain regions such as anterior cingulate gyrus,inferior frontal gyrus,precentral gyrus and middle frontal gyrus is also lower in overweight/obese individuals.In difficult conditions,lower activations were observed in the trial of SS in the orbitofrontal cortex and lateral occipital brain regions of the overweight/obese individuals than the normal individuals;in the trial of LL,the activation of brain regions such as frontal pole,middle frontal gyrus,and precentral gyrus was significantly lower in overweight/obese individuals;The further regions of interest analysis showed that,in the conditions of S>L,L>S and LL,there was a significant negative correlation between anterior cingulate gyrus activation and impulsivity.In LL conditions,negative correlations between brain activation and food addiction were observed in the frontal pole;the inferior frontal gyrus activation was negatively correlated with impulsivity.It indicates that the activation of anterior cingulate cortex,front pole and inferior frontal gyrus may exert key roles in the process of decision impulsivity.In study two,109 college students were recruited,including 49 overweight/obese and 60 control subjects.The Stop-signal task in the food context was used to investigate the ability of inhibitory control.The independent sample T test showed a significant difference between overweight and obese individuals and normal individuals in food stop signal response(SSRT2)and average stop signal response(SSRT).Brain imaging results showed that less activations were observed in food cue condition on the Go response test(Go_food vs Go_nature)in the precentral gyrus,supramarginal gyrus,and precuneus in overweight/obese people than normal individuals.In a successful Stop response test(Stop_food vs Stop_nature),the results indicated that lower activations in overweight/obese individuals was found in response to the food cue compared to normal individuals in the precuneus,supramarginal gyrus and superior frontal gyrus.The further regions of interest analysis showed that,in the Stop_food condition,negative correlations between brain activation and the inhibition ability were observed in right inferior frontal gyrus cortex,indicating that the inferior frontal gyrus play an important role in reaction inhibition.In conclusion: 1)In terms of behavior,overweight/obese individuals exhibited more impulsive characteristics,preferring to choose immediate rewards during intertemporal choice,and had a poor reaction inhibition ability in Stop-signal task.2)In brain imaging,the decision impulsivity was negatively correlate with activation in anterior cingulate gyrus,the frontal pole,and the inferior frontal gyrus,which indicated that decision impulsivity is related to activation of the anterior cingulate gyrus,frontal pole,and the frontal gyrus.Compared with the neutral stimuli,overweight/obese people had less activations in food stimuli in inferior frontal gyrus,the supplementary motor area,and the precentral gyrus,which indicated that the action impulsivity is related to the activation in these brain.These finding may reflect that the frontal lobe exerts advanced control ability in impulsivity.