| As the saying “food is god to the people” goes, eating delicious food is a great pleasure in life for most mortals. Chowhounds and delicious temptation are everywhere. Under the priming condition of delicious temptation, overweight, obesity and eating disorders, which caused by unhealthy eating model, have seriously impact on the daily lives of individuals. Restrained eating(RE) refers to intentional, sustained restriction of caloric intake to lose or maintain body weight. Restrained eating is the marginalized populations of eating disorder, whose symptoms is the most common and critical maladaptive behavior in the development of disordered eating. It has both theory and realistic significance how to succeed in curbing the desire in the obesogenic modern society of tempations. Inhibitory control ability has a closely linked with individual health behaviors, which play a crucial factor whether or not to overeat in food cues for Restrained eater.Based on the balance model of self-regulation, weakened function of conflict monitoring and inhibitory control ability in the prfrontal cortex break the balance of the frontal-subcortical loop, which is the key factor of dieting failure. Numerous studies show that Inferior frontal gyrus(IFG) is the critical areas of dieting success and eating control. Although brain imaging studies in the neural mechanisms of diet control inquiry has an irreplaceable role, but previous studies also have limitations. The brain imaging studies were unable to effectively distinguished that a neural activation is a necessary condition for a certain behavior or just associated with a behavior, which was unable the causal connection. However, in latest years, a new technique, transcranial direct current stimulation(tDCS) can effectively make up for the shortage. tDCS is a non-invasive technique for brain stimulation. tDCS delivers a weak polarized direct current to the cortex via two electrodes: an active electrode which is put on the target site, and a reference electrode that can be placed either over the corresponding contralateral area, or on another cephalic region(e.g. vertex), or over a non-cephalic site(e.g. shoulder). tDCS induces changes in the underlying neural cell membrane potential: anodal stimulation causes membrane depolarization and increases neuronal firing rates, while cathodal stimulation diminishes neuronal activity. In the field of eating, existing tDCS research is more concentrated in healthy individuals, obesity and eating disorder group, stimulate cite is mainly selected in the dorsolateral prefrontal cortex. No application of noninvasive neuro-modulation technology to explore the food-cue inhibitory control of restrained eating. Furthermore, no study explores the influence of stimulating IFG on eating behavior. Existing research conclusion is based on the individual subjective report, a more objective measurement paradigm study is also less. Only one study applying the objective measures of the Go/no- go of research, but the validity of experimental paradigm is still questionable(its ratio of Go vs no – go trail proportion of 1:1).For inquirying the role of inferior frontal gyrus in eating control, application of tDCS technique combined with the inhibitory control tasks under the food cues, explored the effect of tDCS on the inhibitory control function of restrained eating. Study 1 adopting the method of questionnaire, investigated two subgroups of restrained eaters in the trait impulsive control and the food craving. Results confirmed that unsuccessful restrained eaters demonstrated a defects on trait impulsivity, especially in the atteniional impulsiveness and motorl impulsiveness. And the unsuccessful restrained eaters had stronger trait food cravings. Study 2 adopting the active and sham tDCS stimulation(31successful and 32 unsuccessful restrained eaters, respectively), applied the novel food-specific Go/no Go paradigm with the flanker task, which choosed the right IFG as the target brain regions. Experimental task required the subjects to press the key for the letters in the middle screen except the X key, on both sides of the screen with delicious food pictures. Results showed that the numbers of false alarms on No-Go trials didn’t any significant difference between the active and sham tDCS stimulation. Omission errors on Go trail also had no significant difference, as well as the reaction time on Go trail. Moreover, state food craving after the stimulation didn’t go down, On the contrary, up to a certain extent. Study 3 also adopted the same control design, every 29 unsuccessful restrained eaters on the active and sham tDCS stimulation, which stimulated the right IFG similarly. The experiment task was the stop signal task with the food cues. The results showed that compared with sham tDCS stimulation, real stimulation significantly reduced the stop signal reaction time(SSRT)(Longer SSRTs indicate poorer response inhibition and are considered to reflect more impulsivity). RT on Go trail also had no significant difference.This study firstly confirmed that tDCS anode stimulation of IFG can effectively enhance the inhibitory control ability of unsuccessful restrained eaters on the stop signal task under food cues, however no significant effect in the Go/no-Go paradigm. Additionally, stimulating the IFG, state food craving didn’t have significant changes. The current findings were consistent with other tDCS studies on the cognitive research. Other research has found that stimulating the dorsolateral prefrontal cortex with the Go/no- go paradigm has remarkable enhancement effect on task performance. This study first discusses the influences of the tDCS technique on the inhibitory control function for restrained eater. Starting from the unsuccessful restrained eaters, its goal was to improve the inhibitory control ability under food cues by applying the latest means of neuromodulation. In the future study, it can choose other related brain regions combining with fMRI and EEG technology, to further explore the neural mechanism of self-regulation for restrained eating. |
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