Reward Learning Deficit In Internet Gaming Disorder And Its Cognitive Neural Mechanism

Internet gaming disorder is classified as a formal addictive mental disorder by ICD-11,which refers to the impairment of psychological and social functions of individuals due to excessive Internet game activities.Investigation shows that the growing problem of Internet gaming disorder in China has seriously affected the physical and mental health of adolescents,so it is necessary to further investigate its occurrence mechanism.A reward is a positive value representation of a behavior that guides an individual’s behavioral response strategy.The process by which individuals choose to engage in different behavioral responses based on the value of the reward and make adjustments to future reward activities is called reward learning.According to DSM-5,“loss of interests in previous hobbies and entertainment as a result of,and with the exception of,Internet games” is one of the important diagnostic criteria for Internet gaming disorder.It is suggested that Internet gaming disorder may have different reward learning processing mechanisms for gaming and natural rewards,resulting in individuals showing significant behavioral bias to gaming activities,compared with natural reward activities(such as eating,exercising,etc.),which brings serious psychosocial problems.It has been suggested that individuals with Internet gaming disorder have diminished activation of reward learning-related brain regions for monetary rewards,which may be a key mechanism for their abnormal monetary reward processing.However,the previous study neither compared and examined the differences between game and other reward learning,nor did it systematically clarify the mechanisms of reward learning deficit in Internet gaming disorder.Therefore,based on the reward prediction error theory of reward learning,this dissertation,using questionnaire measures,behavioral experimental methods,and event-related potential(ERP)techniques,designed three studies and six sub-studies in an attempt to systematically examine the reward learning deficit and its cognitive neural mechanisms in Internet gaming disorder.Study 1 examined the presence and performance of reward learning deficit in Internet gaming disorder based on a probabilistic reward learning task.40 individuals with Internet gaming disorder and40 healthy subjects were recruited and separately randomly divided into two groups(four groups in total)to participate the corresponding reward learning tasks.Study 1a set up two reward learning tasks with natural and gaming rewards feedback(reinforcement learning),and study 1b set up two reward learning tasks with natural and gaming punishment feedback(extinction learning).Results found that,compared with healthy controls,at the behavioral and cognitive neural levels,individuals with Internet gaming disorder exhibited a significantly diminished response bias and Rew P amplitude to high probability rewards in the natural reward reinforcement learning task(Study 1a),and also a significantly diminished response bias and Rew P amplitude to low punishment rewards in the gaming reward extinction learning task(Study 1b).Study 2 examined the mechanism of natural reward reinforcement learning deficit in Internet gaming disorder.Study 2a set different levels of reward probabilities(high probability: low probability= 3:1)and compared the behavioral performance of 32 individuals with Internet gaming disorder and33 healthy subjects in a highly and a lowly predicted natural reward learning task.The results found no significant difference in response bias between the two tasks for individuals with Internet gaming disorder,while healthy controls showed significantly greater response bias in the natural reward learning task with higher reward prediction than with lower reward prediction.Study 2b set up a natural reward learning task with different value feedbacks and compared ERP responses evoked by high and low value feedbacks in 20 individuals with Internet gaming disorder and 20 healthy subjects.It was found that there was no significantly different neural response of individuals with Internet gaming disorder between the two tasks,while healthy controls induced significantly higher Rew P amplitude and P300 amplitude by high-value reward feedback than by low-value reward feedback.Besides,the Internet gaming disorder symptoms(IGD-20)and P300 amplitude induced by high-value reward feedback significantly predicted individual’s Rew P amplitude.Study 3 examined the mechanism of gaming reward extinction learning deficit in Internet gaming disorder.Study 3a set up a gaming reward learning task and a probabilistic reversal task based on it.The study compared the behavioral performance of 33 individuals with Internet gaming disorder and33 healthy subjects in the gaming reward learning task with reversal prediction.The results found that individuals with Internet gaming disorder had a significantly smaller response bias in the probabilistic reversal learning task than in the gaming reward learning task,whereas healthy individuals did not differ significantly in the response bias between the two tasks.Study 3b set up a gaming reward learning task with negative feedback and compared ERP responses evoked by punishment,error and reward gaming feedback in 20 individuals with Internet gaming disorder and 20 healthy subjects.The results found that the differences in FRN/ERN amplitudes evoked by punishment,error and neutral feedback were not significant in individuals with Internet gaming disorder,while healthy individuals evoked significantly larger FRN/ERN amplitudes by punishment and error feedback,and error feedback-related ERN amplitudes were significantly larger than punishment feedback-related FRN amplitudes.Furthermore,in all three feedback conditions,individuals with Internet gaming disorder induced significantly lower LPP amplitudes compared to healthy controls,and Internet gaming disorder symptoms and error feedback-related LPP amplitudes significantly predicted individuals’ ERN amplitudes.In summary,the main findings of this study are as follows.(1)There are reward learning deficits in individuals with Internet gaming disorder,manifested as reinforcement learning deficit for natural rewards and extinction learning deficit for gaming rewards.(2)Individuals with Internet gaming disorder exhibit insensitivity to the processing of natural rewards with high and low predictions at the behavioral level and insensitivity to the processing of natural reward feedback values at the neural level.The abnormality in the processing of high-value reward feedback is key mechanism underlying the individual’s natural reward reinforcement learning deficit.(3)Individuals with Internet gaming disorder exhibit abnormal processing of gaming rewards with reversal prediction at the behavioral level and insensitive processing of gaming punishment or error feedback at the neural level.The few cognitive resource devoted to error feedback may be an important mechanism for individuals’ diminished error feedback processing.On the one hand,the natural reward reinforcement learning deficit makes individuals with Internet gaming disorder have lower value assessment of natural rewards and behavioral bias towards gaming rewards,thus showing the absence of natural reward activities.On the other hand,the gaming reward extinction learning deficit makes the link between gaming reward to game behavior difficult to fade,and also individuals’ cognitive flexibility is reduced and negative feedback processing is desensitized,making gaming behavior impulsive and compulsive.In theory,this study systematically investigated,for the first time,whether individuals with Internet gaming disorder have reward learning deficits,the manifestations of their reward learning deficits and its mechanisms.It clarified the learning processing of different types of rewards in individuals with Internet gaming disorder to help better understand the occurrence and development of Internet gaming disorder.In practice,it provides theoretical guidance for targeting the enhancement of natural reward activity motivation in individuals with Internet gaming disorder while reducing the motivation of gaming reward activity,and helps to better maintain the treatment effect of Internet gaming disorder in order to return to normal life.